When you start a 16-bit application, you receive an error message similar
to the following:
16 Bit Windows Subsystem - Hidden Console of WOWVDM.
The NTVDM CPU has encountered an illegal instruction. Source
When you receive WOWVDM error messages when starting 16 bit applications,
they may be caused by problems with the Config.nt or Autoexec.nt file.
These files are parsed each time a VDM is started. If there are problems
with these files, you may see error messages such as the above.
Either restore the Config.nt or Autoexec.nt file, or remark (REM) any
nonstandard lines in the existing files to determine which file
is the source of the errors. Remove the offending lines.
Also, check the versions of the Command.com files. The modified date should be the same as the dates of the original installation of Windows.
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.