I'm buying a desktop help!?

It will play old games fine but you will not max them out. On a a intel Atom 1.6ghz and GMA 3150 (wich is worser then a geforce 6) i play old games at around 7-10fps a little choppy but playable most of the time and it runs fine. At your specs i see games running at low res medium-high or high res-low settings. You can also Overclock your GPU in NVIDIA tools buy installing the latest drivers to get better performance