I found some info on this error by searching Usenet newsgroups. Here is a recent answer to someone who described the same kind of problem:

Wesley Vogel Jun 14, 11:20 am show options

Newsgroups: microsoft.public.windowsxp.help_and_support
From: "Wesley Vogel" <123WVogel...@comcast.net> - Find messages by this author
Date: Tue, 14 Jun 2005 09:20:50 -0600
Local: Tues,Jun 14 2005 11:20 am
Subject: Re: 16-bit Windows subsystem error message
Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse

Seems to be an epidemic lately....

This can be caused by a trojan.

Get rid of the trojan.

Update your antivirus software and run a full system scan.

Copy the autoexec.nt file from C:\Windows\Repair to C:\Windows\System32.
And set Attributes for autoexec.nt to Read-only.

Read-only
[[Specifies whether this file is read-only, which means that it cannot be
changed or accidentally deleted.]]

1. Right click the file.
2. Properties.
3. Select: � Read-only.
4. Click: Apply.
5. Click: OK.

16-bit MS-DOS Subsystem error while installing or running a DOS application
http://windowsxp.mvps.org/16bi�t.htm

MS-DOS or 16-bit Windows-based program Error Message
http://www.kellys-korner-xp.co�m/xp_m.htm#16bit

Error message when you install or start an MS-DOS or 16-bit Windows-based
program
http://support.microsoft.com/d�efault.aspx?scid=kb;en-us;3247�67

--
Hope this helps. Let us know.

Wes
MS-MVP Windows Shell/User

In news:33B70BF9-BC82-4B1E-BD37-8A102999DCC5@microsoft.com,
Markatk <mark...@discussions.microsoft�.com> hunted and pecked:

- Hide quoted text -
- Show quoted text -

> Please help. I have been running a french - english dictionary perfectly
> successfully for months on my computer, but today I cannot load it and
> keep getting a message headed 16-bit Windows Subsystem
> C;\WINDOWS\SYSTEM32\AUTOEXE.NT�. The system file is not suitable for
> running MS-DOS and Microsoft Windows
> I then have no choice but to close this message. I have tried running
> System Restore (several times), and going to the properties of the
> Dictionaries and trying every compatability option, with no success. I am
> well beyond the limit of my understanding and expertise now! I have tried
> deleting the programme and reinstalling it from the origin CD but I
> cannot re-install it and receive the original error message. Any help and
> advice greatly appreciated.
> --
> Markatk