That drastic answer may not be the solution, attendant.
Have you updated your spyware/antivirus software and run them in safe mode?
You should at the very least run ewido, spybot and X cleaner which are all free downloads.
Have you cleared your cache and cookies, which can cause your pc to slow down if not done regularly?
Is your fan running properly?
Have a look at your task manager and see if anything is using up all the resources.
Try simple things like the above first.