Do it yourselfers have a bit of a hassle keeping up with 64-bit, Dual Core, and all the different price ranges when buying CPUs for their machines. So much so, many people just buy pre-built systems to save time. But if you're still intent on building the fastest and cheapest systems for your money, head over to Computer Shopper's guide to buying the best CPU. They even have a section on laptops and what CPUs not to buy. [Computer Shopper]