Virtual Device Driver
VxD

    (VxD) A device driver under Windows
   3.x/Windows 95 running as part of the kernel and thus
   having access to the memory of the kernel and all running
   processes as well as raw access to the hardware.  VxD's
   usually have the filename extension .386 under Windows 3.x
   and .vxd under Windows 95.  VxD's written for Windows 3.x can
   be used under Windows 95 but not vice versa.

   (1997-02-27)