Civ5 uses supposedly a custom game engine. The 8800/9800 series is very inefficient in its VRAM usage, that might be the culprit. Do you have 512 or 1024 MB, and at which resolution do you play? Both options are less than optimal for Civ5. Any video card upwards of ~$60 would enable your desktop to run with pretty nice graphics, but it will probably not much fun on anything but tiny/small maps. You probably cannot upfgrade the CPU in a meaningful way. Laptops in general get expensive it you want to run games decently on them, they deliver only about half the performance of a desktop at a given pricepoint. There are a few "which laptop should I buy" thread floating around in this forum and in the Colosseum.