looks like something has deleted or damaged the autoexec file from the system32 folder
there has been spyware recently that deletes this for some reason.
you shouly run some anti spyware software like adaware or spybot before fixing this because it will just do the same again.
in windows 2000 i think the autoexec.nt is in c:\winnt\system32\
(you might need to unhide system files to see it and other system files)
there should be a backup of autoexec.nt in c:\winnt\repair
which you should just be able to copy accross to \system32
there is a solution recommended by miscrsoft which involves copying autoexec.nt from the windows cd >
http://support.microsoft.com/default...b;en-us;324767