>> c:\Windows\system32\autoexec.nt. the system file is not suitable for
>> running MD-DOS and Microsoft Windows applications.
By coincidence I had this error a couple of weeks ago installing some postcode software. It indicates that autoexec.nt is corrupt (it's a config script, nothing to do with VFP).
The following link should sort it out:
http://support.microsoft.com/default.aspx?scid=kb;en-us;324767&Product=winxpGary.