I have two hard drives. One is a 120 GB barracuda, and the other is a 1 TB Western Digital. My OS is installed on the smaller hard drive while the larger one is for storage. So one morning they were both working fine, but later that day it had blue screened and after restarting neither hard drive was detected. I have checked to make sure they spin up and and I have changed the sata connectors. Beyond that I don't really know what else to check.