I have a Dell Inspiron 600M w/ XP purchased three(?) years ago. About six or seven months ago I started getting problems with random fits of extremely slow processing. By this I mean I might be browsing the internet, watching a movie, playing a video game, even browsing my computer, then, out of nowhere, and not related to any specific instance, my comp comes to a snail crawl: the movie gets freakishly and uselessly choppy; my internet browser will not dl any page within two or three minutes; opening any new window, be it through my computer, internet explorer, etc. becomes a daunting task, taking usually minutes to complete; and my video game becomes so choppy that I cannot play it. This is not to say all those programs are running at once; normally I have no more than two programs running (currently IE and Winamp 2.1, audio) at a time, and never combine a movie file with my video games (usually Zsnes, tetris attack, sometimes CivII). Right now everything is working fine, but I usually can't get through 5 minutes of tetris attack or around ten minutes (this can vary greatly) on windows media player. The only program that seems to work fine is Winamp when I play audio only. Usually, though, the slowdown lasts around 10 - 20 minutes, then I'm back up and running. Rebooting DOES NOT affect this. My internet connection is fine. My pagefiling is by all means normal, and doesn't increase during these random fits of slow-down, however my CPU usage sky-rockets from 1-6% all the way to 100% and sits there until it feels like coming back down again. I don't have any viruses or malware or worms/trojans/ad-ware/spyware etc.; I've looked into this and it simply cannot be the case.

Why the random fits of slow-down? Is there anything I can do about it? The problem is completely debillitating, and I'd like to use my computer for more than ten minutes at a time before it becomes effectively useless.