Computers are stupid.

OK, I installed 512 PC2100 in my computer, first it came up 128 megs short (512 + 256 + 256 = 896 = fucked up), after checking to see what chip was messed up, the 128 missing megs finally came back. I rebooted the computer a few times and still showed 1024megs, I was happy. I bring up AIM and I start get errors that the program is corrupted and I should run check desk. Well, it's been a while since I've done that so I thought I had a free afternoon, instead of bettering myself by reading the Tao Te Ching or The Art of War I'll work on my computer. Ran check desk and now I got svchost.exe coming up and eating a meg of memory a second. I tried to installed Service Pack 1 (using XP Pro), and of course it didn't like my serial number. So if anybody knows how to fix this short of being reinstalling XP let me know.