I would use the CPU fan replacement guide to point to which one is for the CPU. That guide is [guide|899|here.] Personally if you are having heat issues I would reapply thermal compound/paste to both the GPU & CPU. You do not apply thermal compound/paste to the heat sink, it is applied to the processor - '''thin as possible, yet still covering'''. A rough guide for applying thermal compound is [guide|744|here.] I recommend using the Arctic silver thermal compound/paste available [product|IF179-010|here.]