I haven't used Norton Utilities in a long time airspro.
My only observation is that anything that wants to run in the background is bad. However, Norton likely has error scanners and defrag routines that work much better than the stock ones. Virus scanners are notoriously bad at causing pauses in gameplay, especially Norton AV. Still, it's not too big a deal to kill the AV tasks before you play. Basically, use any of the utilities that you can run when you need them, and disable any that wan to run in the background all the time.

------------------
Sean "Lephturn" Conrad - Aces High Chief Trainer
A proud member of the mighty Flying Pigs
http://www.flyingpigs.comCheck out
Lephturn's Aerodrome for AH articles and training info!