I installed 10.8 on my imac 27 inch (2009), and a few days later when I rebooted the computer, the apple logo comes and it does not move any further and does not load the rest of the software. Disk utility says it can't repair the disk. I have my files back up on my WD, but not sure if all my itunes and iphoto files are backed. Not sure if WD backs them automatically. I am sure it has. I just can't find them yet.