Again, if you can identify which file is causing the virus to run I recommend start > run> msconfig > startup and uncheck it's box. Is Norton capable of running in safe mode? If so restart your PC in that and try to scan for viruses that way.
Also, what was the name of this website? If nothing else we will probably want to avoid it.
Finally, weather or not you nuke your PC I would still advise switching to Firefox, it will reduce the rate at which you get new viruses and should solve your pop-up problem, also, odds are the virus won't be able to alter Firefox's settings, very few programs ever do.

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