This error message occurring in WinXP is getting wide spread attention recently.

"16 bit Windows Subsystem: C:\WINDOWS\SYSTEM32\AUTOEXEC.NT. The system file is not suitable for running MS-DOS and Microsoft Windows applications. Choose "Close" to terminate the application."

"It turns out that there is some malware going around that's deleting the autoexec.nt file from the \windows\system32 folder. The fix, for now, is to copy the backup autoexec.nt from \windows\repair to \windows\system32 and then to run av and spyware checks with Spybot, AdAware and whatever AV program the user has (all with the latest definitions, of course). I'm not sure if the specific malware has been identified yet, but the above process does seem to solve the problem. Hope your readers can benefit from this." Allan, tweakxp forum administrator, http://www.tweakxp.com/

The above quote is from Fred Langa's excellent twice weekly (free) newsletter, "The Langalist". http://www.langa.com

To see how widespread the problem, see this Google page:
Google Search Results

I hope this will be of some benefit!

Dwight