If you've still got your Windows XP CD, insert it and click the START button, then RUN... and type
expand D:\i386\autoexec.nt_ C:\windows\system32\autoexec.nt
(D:is your CD ROM drive letter)
There's a more detailed solution for running older programs on WinXP at
http://support.microsoft.com/default...b;en-us;324767