Configuring Windows 7 (Training Kit) - Part 24 doc

Lesson 1: Managing Device Drivers and Devices CHAPTER 4 203
Viewing Bandwidth Allocations for a USB Host Controller
Each USB controller has a fixed amount of bandwidth that all attached devices share. If you
suspect a USB controller requires more bandwidth, you can confirm this by viewing the
bandwidth allocations currently being used by each device. In Device Manager, double-click
Universal Serial Bus Controllers, right-click the Host Controller for your system, and choose
Properties. On the Advanced tab, in the Bandwidth-Consuming Devices list, view the
bandwidth used by each device.
Viewing Device Driver Information
To view details about the device drivers that are running on your computer, navigate to the
device whose driver you are investigating, right-click the device, and choose Properties. On
the Driver tab, you can click Update Driver to update the driver, Uninstall to remove it, and
Disable to disable the device. If the driver replaced a previously installed driver, the Roll Back
Driver button is also enabled. To obtain details about the driver, click Driver Details. The
Driver File Details dialog box appears as shown in Figure 4-6, with a list of the individual files
that make up the driver, file version information, and digital signature information.
FIGURE 4-6 Driver details
Installing Devices and Managing Device Drivers
PnP specifications define how a computer detects and configures newly added hardware and
automatically installs the device driver. Windows 7 supports PnP so that when a user plugs in
a hardware device, the operating system searches for an appropriate device driver package,
automatically configuring it to work without interfering with other devices. This makes the
installation straightforward.
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However, users cannot be permitted to plug any device they please into their work
computers. Device driver software runs as if it is a part of the operating system with
unrestricted access to the entire computer, and only authorized device drivers can be
permitted.
When a user inserts a device, Windows 7 detects the new hardware and the Plug and Play
service identifies the device and searches the driver store for a driver package that matches
the device. If a suitable driver is found, the device is considered to be authorized and the Plug

and Play service copies the driver file (or files) from the driver store to its operational location,
typically C:\Windows\Sysrem32\Drivers. The Plug and Play Service configures the registry and
starts the newly installed driver.
Installing Device Drivers from Windows Update
By default, updated device drivers uploaded to Windows Update are downloaded and
installed automatically on a client computer. You can amend this behavior through the Device
Installation Settings dialog box, shown in Figure 4-7. The most straightforward method of
accessing this dialog box is to type device installation in the Search text box on the Start
menu and click Change Device Installation Settings.
FIGURE 4-7 Device Installation Settings dialog box
The default setting is Yes, Do This Automatically (Recommended). However, if you want
to ensure that only device drivers you have tested are installed on the computers running
Windows 7 in your organization, you can select Never Install Driver Software From Windows
Update.
If you choose Always Install The Best Driver Software From Windows Update, Windows 7
will determine automatically whether a new driver is superior to one already installed. However,
you will not be able to test the new driver before installation. Similarly, if you select Only Install
Lesson 1: Managing Device Drivers and Devices CHAPTER 4 205
Driver Software From Windows Update If It Is Not Found On My Computer, you will not be
able to test the new drivers before they are installed. In an enterprise environment, particularly
if software is distributed through Windows Server Update Services (WSUS), driver updates from
the Windows Update site are disabled and the site is removed from the search path.
Staging a Device Driver
If the device driver does not exist in the driver store, then an administrator needs to approve
the device. This process is known as staging. You can configure a computer Group Policy so
that ordinary users can approve the installation of a device in a specific device setup class,
and you can stage a specific device driver so ordinary users can install that device. However,
it would be most unwise to do this for all devices. You learn how to configure Group Policy
to allow non-administrators to install specific devices and device setup classes in the practice
session later in this lesson.

Windows 7 starts the staging process by searching for a matching driver package in folders
specified by the DevicePath registry entry. You learn how to configure Windows 7 to search
additional folders for device drivers in the practice session later in this lesson. If a suitable
driver is not found, Windows 7 searches the Windows Update Web site. Finally, the user is
prompted to insert installation media.
If a driver is found, the operating system checks that the user has permission to place the
driver package in the driver store. The user must have administrator credentials or computer
policy must be set to allow standard users to install the identified device. Windows 7 then
checks that the driver package has a valid digital signature. If the driver package is unsigned
or signed by a certificate not found in the Trusted Publishers store, Windows 7 prompts the
user for confirmation. If the driver is approved by an authorized user, the operating system
places a copy of the driver package in the driver store and installation continues.
Windows performs all the required security checks during staging, including the verification
of administrator rights and the validation of digital signatures. After a driver package has been
successfully staged, any user that logs on to that computer can install the drivers in the driver
store by simply plugging in the appropriate device. There are no prompts, and no special
permissions are required.
Quick Check
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You have four devices plugged into an unpowered USB hub. You have a powered
hub with an empty slot and decide you could improve hardware performance by
transferring one device from the first hub to the second. How to you determine
which of the devices on the unpowered hub consumes the most power?
Quick Check Answer
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Double-click Universal Serial Bus Controllers, in Device Manager. Right-click the
unpowered USB hub and choose Properties. On the Power tab, view the power
required by each device in the Attached Devices list.
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More Info THE DRIVER STORE AND THE STAGING PROCESS

For more information about the driver store and the staging process, see http://technet
.microsoft.com/en-us/library/cc754052.aspx. This is a Windows Server 2008 and Windows
Vista reference, but it also applies to Windows 7.
Installing a Non-PnP Device
If a device is non-PnP (for example an older device), your logged-in account needs to have
administrator credentials for you to install it. If the device comes with installation media,
Microsoft recommends you insert that media and use the installation software it contains.
Typically, you do this before you plug in the device.
Otherwise, open Device Manager, right-click the computer name at the root of the tree in
the details pane, and click Add Legacy Hardware. This starts the Add Hardware Wizard shown
in Figure 4-8.
FIGURE 4-8 The Add Hardware Wizard
The wizard lets you choose whether to scan and search for hardware or to install hardware
you manually select from a list. If you choose the former option, the device needs to be
attached to the computer. The procedure is the same as for staging PnP hardware that has
not been preauthorized.
If you choose to select hardware from a list, you are presented with a list of device
types. If you opt to select All Devices, you can select a device by manufacturer as shown
in Figure 4-9. If you have the driver (but not necessarily the driver installation package) on
removable media or in a folder on your hard disk, you can click Have Disk.
When a driver has been chosen, the wizard installs your hardware. If there are problems
with the hardware (for example, you get a Code 10 error—the device cannot start), these are
listed in the final page of the wizard.
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FIGURE 4-9 Selecting a device driver
Configuring Device Installation Policies
In the practice later in this lesson, you use Local Group Policy Editor to permit non-administrators
to install devices of a specified device setup class. You can also configure other device installation
policies using the same tool. In Local Group Policy Editor, expand Computer Configuration;
expand Administrative Templates, System, Device Installation; and click Device Installation

Restrictions. In the right pane, click Standard to view the Standard tab. This tab contains a list of
policies, as shown in Figure 4-10.
FIGURE 4-10 Device installation restriction policies
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You can use these policies to perform the following actions:
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Permit members of the Administrators group to install and update the drivers for any
device, regardless of other policy settings.
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Enable Windows 7 to install or update device drivers whose device setup class globally
unique identifiers (GUIDs) you specify, unless another policy setting specifically
prevents installation.
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Prevent Windows 7 from installing or updating device drivers whose device setup
class GUIDs you specify. This policy overrides any other policy that permits update
or installation.
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Display a custom message to users in the notification balloon when a device
installation is attempted and a policy setting prevents the installation.
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Display a custom message title in the notification balloon when a device installation
is attempted and a policy setting prevents the installation.
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Specify a list of PnP hardware IDs and compatible IDs for devices that Windows
is allowed to install. Other policy settings that prevent device installation take
precedence over this policy.
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Specify a list of PnP hardware IDs and compatible IDs for devices that Windows
is prevented from installing. This policy overrides any other policy that permits
installation.

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Set the amount of time (in seconds) that the system will wait to reboot to enforce
a change in device installation restriction policies.
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Prevent Windows 7 from installing removable devices. This policy setting takes precedence
over any other policy setting that allows Windows 7 to install a removable device.
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Prevent the installation of devices that are not specifically described by any other
policy setting.
You can open Local Group Policy Editor by entering gpedit.msc in the Start search box. It is
highly recommended that you double-click each of the policies in Device Installation Restrictions
(and in Device Installation) in turn and obtain more details about each. Investigating the policies
in Local Group Policy Editor is one of the suggested practices at the end of this chapter.
Working with Device Drivers
You saw previously that installing a hardware device involved locating the device driver
installation files and installing the driver. Once the driver is installed, you can update it
(by installing a replacement driver), uninstall it, disable it, and enable it. If you have updated
a driver and find that the updated driver does not work as well as the previous driver, you can
roll back to the driver that was installed before the update.
If an updated device driver is distributed through Windows Update, it is typically installed
automatically if you choose to download it. Usually you use the Update Driver functionality
if a new or updated device driver becomes available from a vendor some time before it is
published to Windows Update. To get the latest version of the driver and test it on your
Lesson 1: Managing Device Drivers and Devices CHAPTER 4 209
reference computer running Windows 7, you need to download the driver files from the
vendor’s Web site and then manually update the driver.
When you update a driver, the process is similar to the way a driver is installed when
new hardware is added to the computer. If the driver is already authorized and in the driver
store, or if an administrator it has staged it, the update process, once started, proceeds
automatically without user intervention. Otherwise, you can allow Windows 7 to search for

drivers for the hardware device or you can specify a folder address manually as described in
the previous section, “Installing a PnP Device.” If a driver can be found that is more recent
than that already installed, the administrator is prompted to approve the driver.
You can start the driver update process in Device Manager in two ways:
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Right-click the device and choose Update Driver Software.
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Double-click the device. On the Driver tab, click Update Driver.
You can install a new driver or one that has been updated. If, however, you consider the
current driver installation might be corrupt, updating a driver will not by itself reinstall the
current driver. In this case, you need to uninstall the driver and then go through the process
of installing it again. As with updating a driver, you can either right-click the device in Device
Manager and choose Uninstall, or you can double-click the device and click Uninstall on the
Driver tab. The Driver tab is shown in Figure 4-11.
FIGURE 4-11 The Driver tab
Sometimes, rather than uninstalling and reinstalling a driver, you can solve problems by
disabling it. If you have a driver conflict, you probably need to disable one of the drivers or
stop it if it is a non-PnP device.
You cannot roll back a driver by right-clicking the device in Device Manager. You need
to access the device’s Driver tab. Unless a previous driver has been installed, the Roll Back
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Driver control is disabled. In general, you roll back a driver if you have updated a device
driver but the new driver does not work as well as the previous one or causes conflicts with
other drivers. In this case, the previous driver should still be in the driver store and the process
should take place without user prompts (other than clicking Yes to confirm).
If you are investigating problems with a driver, or if you have any other reason for wanting
to know more about it, you can click Driver Details on the Driver tab. Driver details for
a network adapter driver are shown in Figure 4-12.
FIGURE 4-12 Driver details
Driver details indicate where the working driver file is stored. Note that this is not the driver

store, which is a protected area. It also tells you the file name and type. Working driver files
operate as if they are part of the operating system and typically have a .sys extension. Driver
installation files have an .inf extension. Driver details include the provider (typically third
party), the file version, the Digital Signer (typically Microsoft), and copyright information. It
can often be useful to know a file version if you are having problems with a driver and are
looking for information on the Internet, such as on Microsoft blogs. You might see a message
along the lines of, “Version 10.0.5.3 has this problem. Uninstall it and install version 10.0.5.2.”
Resolving Driver Conflicts
Driver conflicts are much less common than they used to be. It was common 15 years ago
that you connected a printer and your mouse stopped working. Almost all modern hardware
is PnP. The operating system controls installation, and conflicts typically are avoided. However,
no system is perfect, and a conflict could still occur.
Typically a conflict occurs when two devices require the same resources, particularly when
their interrupt or input/output (I/O) requirements clash. You can determine resource usage on
the Resources tab of the device Properties dialog box, as shown in Figure 4-13. In most device
drivers, Use Automatic Settings is selected and Change Settings is disabled.
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FIGURE 4-13 The Resources tab
Conflicts between PnP devices are unusual and can be solved temporarily by disabling one
of the devices. Updating the driver (if an update is available) or uninstalling and reinstalling
the hardware will probably solve the conflict.
Figure 4-14 illustrates a conflict situation in which a non-PnP device uses resources also
used by the motherboard. If a conflict involves a non-PnP device, you may need to stop this
device to resolve the problem.
FIGURE 4-14 A resource conflict
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To stop a non-PnP device, perform the following procedure:
1. Open Device Manager.
2. On the View menu, choose Show Hidden Devices.
3. Double-click Non-Plug and Play Drivers, right-click the device you want to stop, and

choose Properties.
4. On the Driver tab shown in Figure 4-15, click Stop and then click OK.
FIGURE 4-15 The Driver tab for a non-PNP device
The procedure to restart a device is identical except you click Start instead of Stop. You
can also change the Startup Type on this tab. Note that if the Start button on the Driver tab is
unavailable, the driver is already loaded.
Using the System Information Tool to Identify Resource Conflicts
If you suspect that a device driver is working incorrectly because of resource conflicts, you
can view the I/O and IRQ requirements of each device by using the System Information
(Msinfo32) tool. Using a single tool is more convenient than accessing the Resources tab of
each individual device. You start the Msinfo32 tool by entering msinfo32 in the Start search
box, the Run command box, or the command prompt. You do not need to open an elevated
command prompt to run Msinfo32. The tool provides general system information, as shown
in Figure 4-16.
When you expand Hardware Resources, you can view the Memory, I/O, and IRQ resources
used by every device on the computer. However, arguably the most useful information for
resolving conflicts is obtained by selecting Conflicts/Sharing, as shown in Figure 4-17. If you
are having problems with a particular device, you can search for the device by specifying
it in the Find What: box, determining what devices it shares resources with, and identifying
possible conflicts.