Depending on your budget, and how much you can reuse, you can get this done fairly inexpensively. AMD processors and MB's are slightly less expensive, and unless you are hardcore gaming, you won't notice any difference. Depending on if you can fit a standard MB in your case, a reasonable system might look something like this. AMD dual core A4-3400 llano series processor $45, ASROCK A55M-VS FM1 motherboard $48, and 4 gigbyte Crucial Balistic DDR3-1833 ram $45. Video is on the motherboard, and a heatsink is included with the processor. Of course if budget allows, the options are endless.