well, the 600 Mhz processor is located about an inch and a half over and down from the 400Mhz processor I originally had. So, it appears I will have to move the heat sink. Where would I put an aftermarket heat sink and fan? the original heat sink is sandwiched between the chassis and the back side of the main board (only about 1/4 inch). I will try to take some pics as soon as I get my replacement board, as the first one burned up :|