my brother can play half life 2 on mostly medium settings with basically the same specs except his graphics card is like a geforce 4 or somthing so you should do fine with that system.
lol invest yourself in a newer generation graphics card and u can get the full potential out of those games! i usd to have a 5700+ witth my specs (in my sig) and i got it medium, medium high-ish settings now i have high high high high
With that system, that's on the verge of low and medium, with some aa and ap turned on. your frame rate might slow down and you might get some choppines depending on what settings you put it at. But you can the game, oh yeah.