Hey all. My macbook did not turn on one day. It was stuck on the apple sign with the loading pinwheel. I tried to repair the hard drive. No luck. I bought another internal hard drive and it wasnt able to be formatted. It kept giving me a "unable to format last block" error. I figured it was a bad new drive so I bought a different one. The different one i bought gave me unable a different error. I went out and bought an SATA enclosure. I was able to start ALL the hard drives I had on my other mac. I tried to install OS X mountain lion on one of the hard drives in an enclosure and it worked fine. After Mountain Lion was loaded, I put it back into the mac and it did not want to start. It recognized the hard drive in there and everything. but did not start. I then plugged it in externally and it booted fine. Anyone know what the issue could be?