Re: Possible upgrades (please help)
Your computer uses DDR2 ram, any is fine, as for video card, your computer can use PCI-Express which is good but your CPU will bottleneck anything decent.
The best CPU upgrade you can go is a Pentium D, even the best Pentium D 960 will only be fast as a Athlon 64 x2 3800+ or 4000+ which is not so good.
As for ram, if you want to, get another 2gbs, their pretty cheap nowadays.
And for your videocard, you won't want something to high end. x1950GT, x1950 PRO, 7900GS are in the $100 price range and will suit you.
But if you buy a whole new computer, you'll be able to pick faster and yet still cheaper parts and reuse things like the hard drive and the case. Thats what i would recommend.