I'm more or less a total newb when it comes to computers. My computer has an AMD dual core 5050e processor, onboard graphics, and 4GB of ram (don't even know how to figure out what kind), and is running windows vista 64bit. I need to stick a dedicated graphics card in here that would meet a minimum requirement of an AMD 2900 HD. I only have a 300 watt PSU, and upgrading it is not a readily available option at the moment. There aren't really any accessories being run off the PC other then the mouse, keyboard, and disk drives. Is there an AMD graphics card that would fit the bill without overtaxing my PSU? Or do I have no option other then to upgrade my PSU?