I just bought a 2011 Macbook that had Lion 10.7. It was running parallel OS With Windows 7. It was working great until I upgraded to 10.7.2 to get Icloud. I couldn't get Windows to boot and the boot camp askes for a disk of Windows 7 to proceed with trying to do a repair. My question is, can I revert back to my previous OS? Even at that I don't know if I will be able to get Windows 7 boot back.