Like others have mentioned, try using Windows 7 or even XP (if you have already have XP). A fresh reload will usually work wonders for a sluggishly loading PC.
If all you're doing is browsing the Internet and the occasional e-mail, a basic low end setup is fine (with integrated video). I just checked NCIX, and this is their cheapest bundle deal this week at $155:
http://www.ncix.com/products/index.p...s&promoid=1021
Pair that up with 2GB of RAM (or 4GB if you're feeling spendy although it's probably overkill for just browsing) and you'll definitely be under $250 after taxes. Hopefully you've got some buddies to help you out if you're not familiar with assembling a computer. (although it's pretty easy if you take the time to browse through the manuals)