Digital signatures tell you whether a device driver is provided by a legitimate publisher. In Windows 7, Windows Vista with SP1, Windows Server 2008 R2, and Windows Server 2008, new features take advantage of code-signing technologies, and new requirements for security in the operating system enforce the use of digital signatures for some kinds of code.
In many instances, device drivers from vendors are already signed. However, there may be instances where you modify the files include with the device drivers and need to sign the device drivers again. For example, you might need to modify an INF file for a device driver, and then sign the device driver.
Review the following resources to help you resolve device driver signing issues: