Spybot - Weird website, catches some stuff that Ad-aware doesn't, plus a couple other features.
Crap Cleaner - A must-have. Does just what it says. Scan for obsolete registry keys, dead shortcuts, etc. Coolest thing is that you can delete everything off the startup list. Do it. All of it. Windows will automatically start anything that's actually necessary, all that other crap is useless.
CWShredder - Somewhat useful tool to make sure your browsers are healthy.
Delete bullshit - This includes things like Norton/Mcaffee antivirus, that free copy of Quicken that came with your computer, and, in my case, 15 gigs of porn that you saved so you could watch later, but never do.
Defrag and diskclean - defrag while you sleep, your mornings will be brighter.
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Do all of the above at least weekly. I did all of this yesterday (having never done any of it except adaware and defrag) and I have an extra 30 gigs on my hard drive, I cut my running programs down from 92 to 33, my running threads from 600 to 300, I cut my resting ram usage in half, and my boot time is now less than thirty seconds.
Another tip for Firefox users: do downloads take a while to start? Clean up your downloads list. Ctrl+J, then hit the cleanup button. Sounds like a silly thing to have to say, but ex-IE users like me are used to going around clearing temporary folders and shit to fix these kinds of things.
After all that, I was totally in the mood to tweak my lappy further, even though I lack any real knowledge of the Windows architecture. So I found this tutorial on how to change your Start Menu text:

For the hex editing, I used UltraEdit (Note that the tutorial doesn't serve XP. For the .exe-swap part of the job, check out this tutorial, which you might even find more helpful overall).
For those of us who obtain movies of questionable origin whose makers insist on using weird codecs, MPlayer has yet to be stumped in my experience. It's a bit wonky as far as interface goes, but the damn thing will play any video file you throw at it.
So, you can spend less than an hour to make your computer run like new (or better) again. Anyone else have any cool programs I have to have?
Edit: *gasp* 700th post 8)