Windows represents a driver as a driver node, which includes all the software support for a device, such as any services, device-specific co-installers, and registry entries. The services for a device include a function driver and any upper-level and lower-level device filter drivers.
Some devices require a vendor-supplied driver that is designed specifically for that device or one that is designed to support a family of devices. However, other devices can be driven by a system-supplied driver that supports all the devices of a given device setup class. Windows selects the driver that most closely matches the device. If Windows does not find such a driver, it selects from increasingly more general drivers.
How Windows Searches for Drivers
Windows searches in specific locations for drivers that match a device. A driver matches a device if the following are true:
One of the Plug and Play (PnP) device identification strings that is reported by the bus driver for the device matches a device identification string in an INF Models section entry of the driver's INF file.
If the matching device identification string in an INF Models section entry specifies a TargetOSVersion decoration, the decoration matches the operating system version on which the device is to be installed.
For more information about the TargetOSVersion decoration, see Combining Platform Extensions with Operating System Versions.
For more information about where Windows searches for matching drivers, see Where Windows Searches for Drivers.
How Windows Ranks Drivers
Windows creates a list of all the matching drivers and assigns each driver a rank. Windows represents each driver's rank with an integer value that is greater than or equal to zero.
For more information about the ranking process, see How Windows Ranks Drivers.
Starting with Windows Vista, Windows also ranks drivers based on whether the driver is digitally signed. Windows ranks drivers based on a digital signature as follows:
If the AllSignersEqual Group Policy is disabled, Windows ranks drivers that are signed with a Microsoft signature higher than drivers that are signed with an Authenticode signature. This ranking occurs even if a driver that is signed with an Authenticode signature is, in all other aspects, a better match for a device.
If the AllSignersEqual Group Policy is enabled, Windows ranks all digitally signed drivers equally.
Note Starting with Windows 7, the AllSignersEqual Group Policy is enabled by default. In Windows Vista and Windows Server 2008, the AllSignersEqual Group Policy is disabled by default. IT departments can override the default ranking behavior by enabling or disabling the AllSignersEqual Group Policy.
Signatures from a Windows signing authority include the following:
Premium Windows Hardware Quality Labs (WHQL) signatures and standard WHQL signatures
Signatures for inbox drivers
Windows Sustained Engineering (Windows SE) signatures
A WHQL signature for a Windows version that is the same or later than the LowerLogoVersion value of the driver's device setup class
How Windows Selects Drivers
Windows selects the driver with the lowest rank value as the best match for the device.
However, if there are multiple equally ranked drivers that are a best match for a device, Windows uses the driver's date and version to select a driver. The driver's date and version are specified by the INF DriverVer directive that is contained in the driver's INF file.
Windows uses the following criteria to select a driver for a device:
Windows selects the driver that has the lowest rank value as the best match for the device.
For drivers that have equal rank, Windows selects the driver that has the most recent date.
For the drivers that have equal rank and date, Windows selects the driver that has the highest version.
For drivers that have equal rank, date, and version, Windows can select any driver.