So you've got the MoBo out, and now you need to remove the heat sinks. Flip the Xbox upside down, and you should see two X-shaped clamps. To take these off, put a flat head screw driver into the part of the clip that curls back. Now turn counter-clockwise and lift up. You HAVE TO rotate the screwdriver, otherwise you'll bend the clamps. You need to be very careful when you're removing them because if the screwdriver slips it could destroy components around it. After you remove them, set them off to the side because we're going to put them back on in the end.