A. The NT Virtual Dos Machine and the Windows On Windows subsystem are used to run older 16 bit software applications. Below are some trouble shooting steps

  1. Check the Autoexec.nt and Config.nt for anything unusual or anything that can be commented out (in the %systemroot%\system32 directory).
  2. Rename Autoexec.bat (e.g. c:\autoexec.bat).
  3. Check for changes in Win.ini or System.ini, or replace by expanding the original files off of the installation media. (%systemroot% directory)
  4. Rename all other *.ini files if possible
  5. In the Config.nt file, allow only:
    dos=high, umb<br>
        device=%SystemRoot%\system32\himem.sys<br>
        files=60<br>
        shell=%SystemRoot%\system32\command.com /e:4096

If you still have problems checkout Knowledge Base article http://support.microsoft.com/support/kb/articles/q196/4/53.asp which has more information.

These files are also on the Emergency Repair disk so you could just copy the versions from the disk over your existing ones which may fix the problem.

This can also be caused by a virus, for example "NYB" in the boot sector of the machine. (PC has a bootable DOS and a bootable NT partition).