The NTVDM CPU has encountered an illegal instruction. Source
Rename any versions of Command.com that are not of these dates, with the exception of a version of Command.com in the root folder of the boot partition (usually drive C) and the Windows folder if you are dual-booting with Windows 95 or Windows 98.
You should also make sure that there is only one copy of the Windows Command.com file, in the System32 folder.
Article ID: 156687 - Last Review: Feb 19, 2007 - Revision: 1