I know companies would like the public to think that viruses are the cause of all problems, but that rarely is the case. Less than 1% of the computer problems I come across are virus related (what programs like norton would fix). (Spyware/popups/backdoor trojans are a different story though.)
As suggested, I wouldn't use norton. Norton completely takes over your computer and does more harm than it does good. It blocks what you want, and lets through everything you don't. It also hogs up all your system resources by running a huge amount of processes in the background. It's completely unneficent.
Nod32 is one of the best antvirus programs I've come across. There's a reason why huge coprorations use it to protect their servers. Because it works. It's fast, clean, and simple. AVG is also decent.
As far as the reminder popping up, it's probably just norton acting all crazy as usual. They like to harass you if your virus definitions are out of date or subscription expired.
The music is probably skipping because all of your resources are tied up.Close any processes you have running on your computer that you don't need.
You can do a quick spyware check with www.adaware.com
or microsoft antispyware from microsoft.com (figuring you are on a xp based machine)
Uninstall norton. That should free up some memory and get rid of that annoying message. problem solved.