problem installing some programs....autoexec.NT error

Microsoft Windows XP

When I try to install some programs I get this message:

C:\windows\system32\autoexec.NT. The system file is not suitable for
running MS-DOS and Microsoft windows applications. Choose close to terminate.

I found that file in the repair folder too, it's not even in the system32
one. Is there something I can do to fix it? There are about 3-4 programs
that are my best and I can't get them to install anymore.
Just copy it back into System32. Some spywares/virus tend to remove/corrupt
that file and the anti-virus/spyware remover clean up may remove it.

Also check for the "CONFIG.NT" file.
Oh WOW thanks that worked. Now could you answer this, I downloaded the
bootvis to help with my very slow bootup, my win98 was faster, well everytime
I try to run it it stops and says it can't defrag I have to do it manually,
well I did defrag and right after that ran the bootvis again and I still got
the same message......why can't I get the program to work for me.
Microsoft has stated that Bootvis is not an end-user utility . You may want
to "scan" this newsgroup and look for Kelly's replies. Kelly has a web page
with several fixes for XP problems and may include one for yor Defrag
problem.