Try doing "FIX" in Norton. If that doesn't work, try right clicking on each folder under C:\ and do "Scan with Norton Antivirus" (or somethin like that). If it finds a file infected there, scan the folders within that folder until you narrow it down to which files are infected. You may also want to try going to Start -> Run and running msconfig. Look at the Startup tab and see if there is anything suspicious running in there that probably shouldn't be. You can uncheck anything that you don't want running and see how that works for ya.
Sorry for my late reply. Yes I am talking about the registry. Excuse me for not being entirely clear. I was talking about checkin the "RUN" key in the registry for the "Current User" (HKCU = Hive Key Current User) AND "Local Machine" (HKLM = Hive Key Local Machine).
Start the registry editor (START > Run > regedit > OK) and browse to:
HKLM > Software > Microsoft > Windows > Current Version > Run
and the same above but for HKCU.
Check the entries and look for anything particular. There are a few "common" folders on your PC. Which of those is it actually opening? If you are not sure what to do, maybe you could make an EXPORT (File > Export) of the "Run" key and post it here, so we / I could take a look at it.