How To: Fix 'Autoexec.nt - The system file is not suitable for running MS-DOS and Microsoft Windows applications'
Applies to: Microsoft Windows XP
When you try to run certain programs you receive an error message like this: Autoexec.nt - The system file is not suitable for running MS-DOS and Microsoft Windows applications.
One of the files config.nt, autoexec.nt or command.com have gone missing from the System folder (C:\Windows\System32) or one of the files config.nt or autoexec.nt is invalid. The problem may have been caused by an installation / setup program, or by a virus or spyware.
Using Windows Explorer, navigate to the folder C:\Windows\Repair, select autoexec.nt and config.nt, then right-click and select Copy. Now go to C:\Windows\System32, right-click some empty space in the folder window and select Paste. This will overwrite the current versions of these files with backup copies.
Click Start, Run, type msconfig and hit Enter. When the System Configuration Utility starts, click the button captioned Expand File.... In the Expand One File from Installation Source dialog box type the name of the file you want to restore (e.g. autoexec.nt), select the location to restore from (this will either be your Windows XP CD or a folder named i386 on your hard disk) and enter the name of the folder where the restored file should go (this is normally C:\Windows\System32). Then click Expand.
Note: Because the problem may have been caused by a virus or spyware, it is advisable to scan the system for both using up-to-date anti-virus and anti-spyware products such as Kaspersky AntiVirus and Spyware Doctor.