I run my computer with a Mr. Fusion home energy reactor. No more plutonium for me!
Obligatory jokes aside, I reiterate lots of stuff. Open msconfig and uncheck most everything that doesn't say Microsoft. I only have 4 icons next to my clock in XP, two of them are for sound, one antivirus/antispyware, and one I haven't used a while and could stand to remove. Sweep for viruses and spyware every once in a while, defragment after large installs (or just occasionally if you don't install big things), run checkdisk... whenever (I actually do maintain my computer, but on anywhere near the rigid schedule some of you do), uninstall things you aren't using, and you ought to running fine until your computer's horribly out of date.