The usual 15 answers to from 5 people to one problem.
Follow the procedure
here to the letter and I would be surprised if you cannot cure the problem.
The suggestion that Norton is good on a powerful PC is like saying you can tow a caravan with anything but best buy a big powerful car. Norton takes over a PC and most people with experience of these things will not touch anything with Norton in the name with a barge pole. Reloading the OS is unnecessary in the majority of cases of virus problems.