We know that a VxD file contain driver for hardware on windows. But what exaclty is as vxd.

Is it like a DLL which containt fonctions that we can use to talk to the hardware, does it have to be register or you can copy it without problem, etc.

I am asking the question because we have a VxD file that as grown from 900k to 2.2M. We think may be a virus did that but we'd like to know more about VxDs.

Thanks.