Have you trying installing Norton again after you re-installed XP?
If you still have problems I would suspect that your copy of Norton is not good, and for that reaosn is not working.
I had to fix once a problem, where an instalation of Norton got stuck in the rebooting and that completely messed up the registry. For example, I could install Norton again without it detecting there was already Norton running. And if I went to the control panel>Add/Remove programs nothing would be listed there
That was a problem from Norton that gave this person an update for Norton, when he needed the full product.
Anyway, it shoudl install well now in your PC, right?