system.drv

Windows driver module

A .drv file is a driver module on Windows. The file is a DLL in the PE format. The extension comes from 16-bit Windows, where all drivers used it. Modern Windows keeps it for some user-mode multimedia components, for example wdmaud.drv and msacm32.drv. Kernel drivers use the .sys extension in its place.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.