Time for a reformat

For the past 2 weeks, my computer has been pis*ing me off. The CPU has been running at 100% constantly, svchost.exe has been running at about 15k which is abnormal and everything from opening a file to locating one, IE browser window lockups when pressing _blank links. Causes are most likely:

  1. Norton Subscription ended
  2. Havent installed sp2 yet
  3. Loads of crap.
    This friday is going to be judgment for my computer. Uninstall everything and put back things i really need only.

One thing though, Im going to install my sp2 cd. Should I install it straight after I reformat or after when I install the basic software applications back up like Microsoft Word, Dreamweaver, etc. ?