My system is slow or infected?

Right after boot up, I am unable to run any program until 5 minutes. When I double click any icon, my mouse cursor turns to an hour glass for a moment and then nothing happens. If I try this on several different programs, same thing happens. After about 5 minutes, everything I have double clicked pops up and computer starts running normal. This problem started a few days ago and I am unable to trace any reason for this problem.
I am using Windows XP with 2.6 Processor and 1GB RAM.
