When did this start happening ?
Have you tried a System restore to before this point.
When was the last time you did some system mantenance and generally tidied things up ??
How many processes are you running while the system is idleing, around 30-40 is OK anything more is excessive and will be causing you problems.
In my experience Norton and XP cause more problems then they solve.
You would be better off removing Norton completely and installing another anti virus system. It's best to try and avoid the All-in-one systems and go for seperate Anti virus (Try
AVG), Anti spyware (Try
Spybot) and Firewall (Try
Zonealarm ).
Please let use know anthing else you think may help.