It's good enough for games. However, the rest will limit your computer:
1. Try to at least get 1GB of RAM
2. the 7600GS or the 7600GT are much better graphics cards, even though they are a little more expensive
I have 2gb of ram (bit of overkill lol) but i have the Gigabyte 7600GS Graphics card. It Runs HOT (70 degress) But it is a awsome card, before doing this i was running Quake 4 On Extreme graphics and still getting around 60fps...
Is it a 6600GT or 6600?? If it's a 6600GT, you should buy a 7600GS, which is as performant as a 6600GT, but more recent. 7600GT is better, but with about 160$, you can buy a X1900GT, more performant than a 7600GT for the same price.