best bet is to go on Newegg and start from scratch. Because in order to "upgrade" your current PC to be able to game, you'll more than likely have to buy a new motherboard, in which case you'll need a graphics card and depending on what your stock PC's power supply supports, you might have to buy a new power supply. Granted if you have like 4-6GB of RAM, you can go on that for the time being. It also depends on what processor your currently have as well.