No acces to DOS-files

This morning I had download some updates for Windows 2000 and now if I want
to go to MS-DOS programs he gives an error that I don's have acces to
DOS-programs..
The are is:

16-bits MS-DOS-subsystem

C:\BACKUP~1\WINDOWS.000\STARTM~1\MS-DOS~PIF
C:\WINNT\system32\autoexec.nt. The systemfile is not good for MS-DOS and
Microsoft Windows-"toepassingen."
Choice close to close this program.

I translated it from Dutch to english, I hope this will be the error to for
Windows in English.
Can somebody help me with this problem?
Does anybody know how this could happen after updating Windows?