I just don't know... All I remember was shutting down the PC to remove the AIO Cooler to apply new thermal paste. After I turned it back on it wouldn't boot. At first I thought it was the Mobo. So I Rma'd for a new one . Still wouldn't post. I RMA'd the CPU, PSU, and a different memory sticks. Flash latest bios, Hard CMOS reset, using stock cooler. Unplugged boot devices and GPU. I tried everything and it still wont post.