Formatting is fun. I bought a new hard drive a couple months ago, because my other one was failing (and it froze upon start up 3x in a row, so I decided it was time...) so I attached that HD, and installed windows 98 on it. Don't ever install Windows 98 unless you have the drivers-- I now know from experience. I didn't have the drivers for my network card, so I couldn't get online to download any other drivers.
I was completely screwed, until I just decided to suck it up and install XP pro (had the CDs from when I bought them for $25 a year ago through the university discount). Bam. Automatically installed everything, updated the drivers, and my comp was all of a sudden, smoove. Nothing like starting your computer and knowing there's NOTHING on it that shouldn't be.