Get better RAM for a start. 1Gb at least, 2 or more if you can.
Get a good graphics card too. I just bought a new computer and it came with 2 512Mb graphics cards inside it as standard (which isn't bad, but won't run counterstrike or anything too well, but I don't play games like that anyway, so it doesn't bother me). My computer was pretty cheap too (about $1000, it's got 4Gb RAM, 2 512Mb gfx cards, loads more stuff I could go on about) so it's not like your going to have to pay too much for just the RAM and gfx card
