HAI!

I just have this error when I’m trying to install ATI and Nendo Demo that I just download:

"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."

Is this the problem that I can't install any programs in CD or DVD?
And another thing, do I need to install XP SP2 because when I install it my computer is slowing down and I can't open any of this website anymore. Is there any way to solve this problem?

Thank U! ^_^