To gain access to the debugging commands for the VMM and virtual devices, you must install the debugging version of WIN386.EXE. You install this file by copying it to the Windows SYSTEM directory. You must exit Windows, save a backup copy of the existing, retail WIN386.EXE file, and copy the debugging WIN386.EXE to the directory.
You should also copy the WIN386.SYM file to the SYSTEM directory and specify this file with the /s option when you start WDEB386. The symbol file contains the service, procedure, and other names that make debugging easier.