Working with Device in Vista

For each hardware component installed on a computer, there is an associated device driver. The job of the device driver is to describe how the operating system uses the hardware abstraction layer (HAL) to work with a hardware component. The HAL handles the low-level communications tasks between the operating system and a hardware component. By installing a hardware component through the operating system, you are telling the operating system about the device driver it uses, and from then on, the device driver loads automatically and runs as part of the operating system.

Device Driver Essentials

Windows Vista includes an extensive library of device drivers. In the base installation of the operating system, these drivers are maintained in the file repository of the driver store. Some service packs you install will also include updates to the driver store. You can find drivers in the FileRepository folder under %SystemRoot%\System32\DriverStore. The DriverStore folder also contains subfolders for localized driver information. You'll find a subfolder for each language component configured on the system. For example, for localized U.S. English driver information, you'll find a subfolder called en-US.

Every device driver in the driver store is certified to be fully compatible with Windows Vista and also digitally signed by Microsoft to assure the operating system of its authenticity. When you install a new Plug and Play compatible device, Windows Vista checks the driver store for a compatible device driver. If one is found, the operating system automatically installs the device.

Every device driver has an associated Setup Information file. This file ends with the .inf extension and is a text file containing detailed configuration information about the device being installed. The information file identifies any source files used by the driver as well. Source files have the .sys extension. Drivers are also associated with a component manifest (component.man) file. The manifest file is written in extensible markup language (XML), includes details on the driver's digital signature, and might also include Plug and Play information used by the device to automatically configure itself.

Every driver installed on a system has a source (.sys) file in the %SystemRoot%\ System32\Drivers folder. When you install a new device driver, the driver is written to a subfolder of %SystemRoot%\System32\Drivers, and configuration settings are stored in the registry. The driver's .inf file is used to control the installation and write the registry settings. If the driver doesn't already exist in the driver store, it does not already have an .inf file or other related files on the system. In this case, the driver's .inf file and other related files are written to a subfolder of %SystemRoot%\System32\ DriverStore\FileRepository when you install the device.

Using Signed and Unsigned Device Drivers

Every device driver in the driver cache is digitally signed, which authenticates the driver as having passed extensive testing by the Windows Hardware Quality Lab. A device driver with a digital signature from Microsoft should not cause your system to crash or become unstable. The presence of a digital signature from Microsoft also ensures that the device driver hasn't been tampered with. If a device driver doesn't have a digital signature from Microsoft, it hasn't been approved for use through testing, or its files might have been modified from the original installation by another program. This means unsigned drivers are much more likely than any other program you've installed to cause the operating system to freeze or the computer to crash.

To prevent problems with unsigned drivers, by default, Windows Vista warns you when you try to install an unsigned device driver. Windows can also be configured to eliminate this warning or to prevent unsigned drivers from being installed altogether. To manage device driver settings for computers throughout the organization, you can use Group Policy. When you do this, Group Policy specifies the least secure setting using one of three configuration settings. These settings are:

• Ignore Use this setting to allow users to install any unsigned driver without having to see and respond to a warning prompt.

• Warn Use this setting to prompt users each time either to continue with the installation of an unsigned driver or to stop the installation.

• Block Use this setting to prevent users from installing unsigned driver software.

Note

When Group Policy is set to Ignore or Warn, unsigned drivers can be installed. When Group Policy is set to Block, unsigned device drivers can't be installed without first overriding Group Policy.

You can configure device driver–signing settings on a per user basis using the Code Signing For Device Drivers policy. This policy is located in User Configuration\Administrative Templates\System\Driver Installation. When you enable this policy, you can specify the action to take as Ignore, Warn, or Block. Once enabled, the system doesn't implement any setting less secure than the established setting.

Tip

If you're trying to install a device and find that you can't install an unsigned driver, you should first check the System utility settings for driver signing. If you find that the settings are set to Block and you can't change the setting, the Code Signing For Device Drivers policy has been enabled and set to Block in Group Policy. You must override Group Policy to install the unsigned device driver.

Tracking Driver Information

Each driver being used on a system has a driver file associated with it. You can view the location of the driver file and related details by completing the following steps:

1. Start Computer Management. In the Computer Management console, click the plus sign (+) next to the System Tools node.

2. Select Device Manager. You should now see a complete list of devices installed on the system. By default, this list is organized by device type.

3. Right-click the device you want to manage and then select Properties. The Properties dialog box for that device opens.

4. In the Driver tab, click Driver Details to display the Driver File Details dialog box. As shown in Figure 1, the following information is displayed:

   • Driver Files Displays the full file path to locations where the driver exists

   • Provider The creator of the driver

   • File Version The version of the file

   
   Figure 1: The Driver File Details dialog box displays information on the driver file locations, the provider, and the file versions.

Installing and Updating Device Drivers

To keep devices operating smoothly, it's essential that you keep the device drivers current. You install and update drivers using the Found New Hardware, Add Hardware, and Update Driver Software Wizards. By default, these wizards can search for updated device drivers in the following locations:

• On the local computer

• On a hardware installation CD

• On the Windows Update site or your organization's Windows Update server

In Group Policy, several policies control the search possibilities.

• Turn Off Access To All Windows Update Features under Computer Configuration\Administrative Templates\System\Internet Communication Management\Internet Communication Settings If this policy setting is enabled, all Windows Update features are blocked and not available to users. Users will also be unable to access the Windows Update Web site.

• Turn Off Windows Update Device Driver Searching under Computer Configuration\Administrative Templates\System\Internet Communication Management\Internet Communication Settings By default, Windows Update searching is optional when installing a device. If you enable this setting, Windows Update will not be searched when a new device is installed. If you disable this setting, Windows Update will always be searched when a new device is installed, if no local drivers are present.

• Turn Off Windows Update Device Driver Search Prompt under Computer Configuration\Administrative Templates\System\Driver Installation If you disable, or do not configure, Turn Off Windows Update Device Driver Searching, this policy setting affects whether a search prompt is displayed for Windows Update of device drivers. If this policy setting is enabled, administrators aren't prompted to search Windows Update and the search will or will not take place automatically based on the Turn Off Windows Update Device Driver Searching setting. Otherwise, administrators will be prompted before Windows Update is searched.

• Configure Driver Search Locations under User Configuration\Administrative Templates\System\Driver Installation If this policy setting is enabled, users can be restricted from searching floppy disk drives, CD drives, Windows Update, or any combination of these locations.

You can install and update device drivers by completing the following steps:

1. Start Computer Management. In the Computer Management console, click the plus sign (+) next to the System Tools node.

2. Select Device Manager in the Computer Management console. You should now see a complete list of devices installed on the system. By default, this list is organized by device type.

3. Right-click the device you want to manage and then select Update Driver. This starts the Update Driver Software Wizard.

   Best Practices

   Updated drivers can add functionality to a device, improve performance, and resolve device problems. However, you should rarely install the latest drivers on a user's computer without first testing them in a test environment. Test first, then install.

4. As shown in Figure 2, you can specify whether you want to install the drivers automatically or manually by selecting the driver from a list or specific location.

   
   Figure 2: Choose whether to install automatically or manually.

5. If you elect to install the driver automatically, Windows Vista looks for a more recent version of the device driver and installs the driver if found. If a more recent version of the driver is not found, Windows Vista keeps the current driver. In either case, click Close to complete the process and then skip the remaining steps.

6. If you chose to install the driver manually, you'll have the opportunity to do one of the following:

   • q Search for the driver If you want to search for drivers, click Browse to select a search location. Use the Browse For Folder dialog box to select the start folder for the search and then click OK. Because all subfolders of the selected folder are searched automatically, you can select the drive root path, such as C, to search an entire drive.

   • q Choose the driver to install If you want to choose the driver to install, click Let Me Pick From A List Of Device Drives On My Computer. The wizard then shows a list of compatible hardware. Click the device that matches your hardware. To view a wider array of choices, clear the Show Compatible Hardware check box. You'll then see a full list of manufacturers for the type of device you are working with. As shown in Figure 3, scroll through the list of manufacturers to find the manufacturer of the device, and then choose the appropriate device in the right pane.

   
   Figure 3: Select the appropriate device driver for the device you're adding.

   Note

   If the manufacturer or device you want to use isn't listed, insert your device driver disk into the floppy drive or CD-ROM drive and then click the Have Disk button. Follow the prompts. Afterward, select the appropriate device.

7. After selecting a device driver through a search or a manual selection, continue through the installation process by clicking Next. Click Close when the driver installation is completed. If the wizard can't find an appropriate driver, you'll need to obtain one and then repeat this procedure. Keep in mind that in some cases you'll need to reboot the system to activate the newly installed or updated device driver.

Restricting Device Installation Using Group Policy

In addition to code signing and search restrictions, Group Policy settings can be used to allow or prevent installation of devices based on device type. The related policy settings are found under Computer Configuration\Administrative Templates\ System\Device Installation\Device Installation Restrictions and include the following settings:

• Allow Administrators To Override Device Installation Restriction Policies

• Allow Installation Of Devices That Match Any Of These Device IDs

• Allow Installation Of Devices Using Drivers That Match These Device Setup Classes

• Prevent Installation Of Devices Not Described By Other Policy Settings

• Prevent Installation Of Devices That Match Any Of These Device IDs

• Prevent Installation Of Removable Devices

You can configure these policies by completing the following steps:

1. Access policy for the appropriate domain, site, or organizational unit (OU).

2. Expand Computer Configuration, Administrative Templates, System, Device Installation, Device Installation Restrictions.

3. Double-click the appropriate policy to view its properties dialog box.

4. Set the state of the policy as Not Configured if you don't want the policy to be applied, Enabled if you want the policy to be applied, or Disabled if you want to block the policy from being used (all as permitted by the Group Policy configuration).

5. If you are enabling the policy and it has a Show option, click the Show button to use the Show Contents dialog box to specify which device IDs should be matched to this policy. Click OK.

6. Click OK.

Rolling Back Drivers

Sometimes you'll find that a device driver that you've installed causes device failure or other critical problems on a system. Don't worry: You can recover the system to the previously installed device driver. To do this, follow these steps:

1. If you are having problems starting the system, you will need to boot the system in Safe mode.

2. Start Computer Management. In the Computer Management console, click the plus sign (+) next to the System Tools node.

3. Select Device Manager in the Computer Management console. You should now see a complete list of devices installed on the system. By default, this list is organized by device type.

4. Right-click the device you want to manage and then select Properties. This opens the Properties dialog box for the device.

5. Click the Driver tab and then click Roll Back Driver. When prompted to confirm the action, click Yes.

6. Click Close to close the driver's properties dialog box.

Note

If the driver file hasn't been updated, a backup drive file won't be available. In this case, the Roll Back Driver button will be disabled and you will not be able to click it.

Removing Device Drivers for Removed Devices

Usually when you remove a device from a system, Windows Vista detects this action and automatically removes the drivers for that device. However, sometimes when you remove a device, Windows Vista doesn't detect the change and you must remove the drivers manually. You can remove device drivers by completing the following steps:

1. Start Computer Management. In the Computer Management console, click the plus sign (+) next to the System Tools node.

2. Select Device Manager in the Computer Management console.

3. Right-click the device you want to remove and then select Uninstall.

4. When prompted to confirm the action, click OK.

Uninstalling, Reinstalling, and Disabling Device Drivers

Uninstalling a device driver uninstalls the related device. When a device isn't working properly, sometimes you can completely uninstall the device, restart the system, and then reinstall the device driver to restore normal operations. You can uninstall and then reinstall a device by completing the following steps:

1. Start Computer Management. In the Computer Management console, click the plus sign (+) next to the System Tools node.

2. Select Device Manager in the Computer Management console. You should now see a complete list of devices installed on the system. By default, this list is organized by device type.

3. Right-click the device you want to manage and then select Uninstall.

4. When prompted to confirm the action, click OK.

5. Reboot the system. Windows Vista should detect the presence of the device and automatically reinstall the necessary device driver.

To prevent a device from being reinstalled automatically, disable the device instead of uninstalling it. You disable a device by right-clicking it in Device Manager and then selecting Disable.