You would need a motherboard, processor (make sure it is the same socket as the motherboard., case, RAM, a video card (since it is a gaming computer), a power supply, a hard drive and optical drive. Also a mouse, keyboard, and monitor if you don't have one. An aftermarket heat sink and fan is highly recommended if you plan on overclocking. Case fans come with the case but there are optional slots on some cases which you could buy extra fans for. Also you can upgrade the case fans if you want things like LED lights.