When was the last time u done the following?
1. Check for startup items in windows msconfig, if so take out some programs you do not need, this will speed up the startup process.
2. When did you last clean the inside of your case? Use an Aircan to get rid of the dust from the fans.
3. When did you last do some housekeeping?
What Antivirus and Spyware do you have on your computer? Do you have ccleaner installed?
come back to us.