Once the $10 heatsinks are freed from the $200-some motherboard, you need to remove the 1/4 inch thingamabobs (X-clamp posts). Use a 1/4 inch nut driver, wrench, or adjustable wrench to get them off. Sit them and the X-clamps in a bag/parts drawer; you won't be needing them again. Take a metal scrubber and remove the thermal gunk from the heatsinks. And, while we're at it, get a toothpick and carefully scrape the gunk off the CPU and GPU. Nothing better than powering on a reborn 360 with clean heatsinks, no?