NTVDM.EXE is the 16-bit subsystem, or WOW (Windows on Windows) execution engine on Windows NT/2000/XP that allows you to run 16-bit Windows 3.1 programs. As a parallel, OS2.EXE is the OS/2 execution engine. 32-bit programs do not run under NTVDM.EXE. A 32-bit program may spawn NTVDM.EXE if the 32-bit program starts a 16-bit program.
This was first published in June 2002