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The second most common USB snafu is that support for USB hasn't been enabled at the BIOS level. In this case, Windows XP doesn't even see the USB host controller in the Device Manager tree.
For more on USB configuration rules, please see Chapter 8.
The problems you're likely to run into here usually result from one of three things:
* The display adapters aren't on the right bus or buses. AGP and PCI are the only ones that work.
* The BIOS is trying to set your secondary display as the system's primary display. A simple BIOS setting change should fix this one in short order.
* You're trying to use an adapter for a secondary display when that adapter is only certified by Microsoft for use with a primary display. Check the Hardware Compatibility List (HCL) for details.
Curing and preventing device problems
As seasoned Windows troubleshooters have known for years, many problems find their solution in an updated or patched device driver. In Windows XP Professional, you can update device drivers several different ways, and - even better - you can control whether non-Microsoft drivers can even infiltrate your PC in the first place. XP adds the ability to roll back to a previous device driver, if one exists.
Here are some of the more common ways that you can update a device driver:
* Double-click a driver in the Device Manager display (get to Device Manager via the System control panel or the Computer Management console), click the Driver tab and then click the Update Driver button. This procedure activates the Hardware Update Wizard, which gives you various choices for hunting new drivers (see Figure 15-3).
Figure 15-3: The Hardware Update Wizard lets you choose where to look.
* Open the relevant control panel for the device you want and update the driver from there. For example, choose the Settings tab of the Display control panel, and then click Advanced, Adapter, Properties, Driver, and Update Driver. (As an exercise, try finding the driver update option in the Sounds and Audio Devices control panel.)
* Choose Windows Update from the Start menu to connect to the Microsoft update Web site, and follow the prompts to update a driver if one's available. This method is really intended primarily for updating Windows XP system files as opposed to device drivers, but you can update select drivers this way. Note that you can't use Netscape or any other non-ActiveX browser to use Windows Update, because it uses an ActiveX control to inventory your machine and recommend updates.
* Run a vendor-supplied EXE program or INF file (which you would right-click and choose Install).
Instant Answer For the exam, know the difference between Windows Update and Windows Catalog. (They appear next to each other on the All Programs menu.) Windows Update lets users update system files with security patches and bug fixes from the Microsoft Web site. Windows Catalog takes you to a marketing site where Microsoft promotes Windows-compatible products.
Driver signing (not by famous golfers)
Microsoft brands a digital signature into the core operating system files and drivers that it ships with Windows XP, as well as files and drivers released subsequently that have passed testing at Windows Hardware Quality Labs (WHQL). That way, Windows XP can 'tell' when a program installation tries to replace one of those core files with a version not 'signed' by Microsoft. (Microsoft has stated that all files that appear on the Windows Update Web site will be cryptographically signed, too.)
The Registry contains settings that govern how Windows XP behaves with respect to driver signing. If you want to see the settings in the Local Security Policy utility, look up Devices: Unsigned driver installation behavior and Devices: Unsigned non-driver installation behavior under Security Settings\Local Policies\Security Options.
Instant Answer You can set the behavior options on an individual PC through the System control panel's Hardware tab by clicking the Driver Signing button to display the dialog box shown in Figure 15-4. If you have administrative privileges on the machine, you can make one setting the default for all users who log on to the PC; otherwise, the setting you make is only effective for the currently logged on user, and if you log on later with a different account, the setting may be different. The three behaviors, which activate upon an attempt to install a new driver or software component, are as follows:
Figure 15-4: Setting options for driver signing.
* Ignore: Unsigned drivers may load without notification.
* Warn: Unsigned drivers prompt a warning message to the user.
* Block: Unsigned drivers may not install.
Instant Answer If a domain-based policy exists for driver signing, it takes precedence over any setting you may make with the Local Security Policy console.
Drivers aren't the only files that have digital signatures in Windows XP. System protected files are the 1,800-plus files for which the Windows File Protection system keeps duplicates in the C:\WINDOWS\SYSTEM32\DLLCACHE folder. The idea is that Windows can restore the original copies from the DLLCACHE folder if the "live" ones become corrupted, overwritten, or destroyed. Two utilities enable you to explore signed system files: SIGVERIF and SFC.