Sounds like a Virus has dropped it's load and is trying to load it on boot-up, it could be the case that Norton has squashed it, but it's still trying to load up.
If your confident, backup your registry, go into Regedit and search for system32.exe - check where it finds those entries, esp looking for stuff like 'RUN=', and remove each entry. Also check your entire PC for the file system32.exe and also check over your startup programs for any shortcuts to system32.exe.
If your lucky you'll get rid of it cleanly, if your unlucky (like worst case here) the virus will have taken some file associations, like .exe and will kill your windows install.
Van-B
Muhahahahaha.