Make sure you've installed your new drivers and removed your old ones. Secondly, the rest of your rig is really, and I mean really pushing it on what it can handle. I'm going to be perfectly blunt here, your motherboard is a heap of shit, as is your RAM. The 2 biggest problems though are your PSU and your Processor. Your GPU, to lay it out clearly, isn't strong enough to power your new Graphics card. In addition, you're not going to get much out of it at all due to the incredibly low output of your CPU, and it's going to be bottlenecked to hell and back. I know this is going to sound insane, but I'd honestly suggesting scrapping your entire rig, and starting from scratch. What we have here is you dropping a Jet engine into a rusty bicycle. It's not going to work out, and it can possibly damage your new card.