You would have to find a barebones laptop that comes with the chassis, lcd, power brick, and motherboard. Then you would just buy your own CPU, ram, video card, etc. Every time I looked into it further it usually just ended up costing about the same as the prebuilt, parts are much harder to find and the warranties usually suck. With laptops you can't really just buy a diferent motherboard to throw in your old laptop they are built specifically for a certain chassis.