Anemic PC

My Dell PC (XP SP2) suddenly slowed to an anemic pace. It takes F O R E V E R to do anything with it. I called Dell tech support, and they suggested trying CounterSpy. It took me F O R E V E R but I finally was able to get the Safe bootup w/network support and to be able to download it. It took F O R E V E R to get it installed (it rejected many times), but now it hangs up. My other spyware programs (Spy Sweeper, AdAware, Spybot) all are similarly stymied. I have a 2nd HD on this PC, so I’ve been attempting to migrate my data files over there (they’re not backed up), but thus far haven’t been successful. I cannot get Windows Update to run (yet). Any other ideas???