A+: Driver Signing

Windows device driver files are digitally signed by Microsoft to ensure quality, using an encrypted file segment which can be checked by Windows. The digital signature ensures that the file has met a certain level of testing, and that the file has not been altered. 

In Windows Vista, driver signing is configured automatically, and in Windows Vista and XP, only administrators can install unsigned drivers. In Windows XP, driver signing can be configured to either ignore device drivers that are not digitally signed, display a warning when Windows detects device drivers that are not digitally signed (the default behavior), or prevent installing device drivers without digital signatures. To configure driver signing in Windows XP, open the System Properties window, click the Hardware tab, and select Driver Signing.