Is this computer any good for gaming?

Assuming it's DDR3 RAM... which it must be to fit on the motherboard that holds the i5 650 then it's a good rig apart from the GFX card which really needs updating, and your PSU is far to small if you want to game with it, I suggest you build your own PC. It's easy to do, cheaper and it's set up just the way you want it to be.