Dude. There's no point in upgrading that computer. To get even a semi-decent performance, you'd need to get a new motherboard and CPU which, coupled with a new GPU and RAM, means almost an entirely new computer. If you want to get a new GPU, you'll also need to get a new power source, as I can imagine that the one you have is equally old. You're looking at around a 300$ config, which is semi-decent, something like this.