I always get stuck in the upgrade trap. I'll set out to upgrade one or two components, next thing I know I'm putting together a whole new computer -- and while I'm at it I might as well pick up a new case and psu.

One thing to note when your planning your upgrades, the memory you'd use on your current board probably isn't going to be compatible with a new motherboard. So don't upgrade the memory first if you plan on getting a new MB/Processor in the future. (184pin ddr vs. 240pin ddr2)

Plus anything over 3gb memory, you'd need a 64bit os. otherwise you'll only see 3ish of your 4gb. Don't forget to budget that.

If your on a tight budget, go with a video card first. you could carry it over to a new computer build if you wanted (pci express x16) and any old $100 card is going to be better than what you have now I'd guess. Easy install too.