I have a Mac OS X 10.6.4 installation on a Macbook Pro 5,1. I use two separate hard drives, one for Windows and the other for Mac. I accidentally switched from Windows to Mac with Windows in sleep mode. When I opened the computer, Windows resumed and BSoD'd. I panicked and forced the computer to shut down. It wouldn't boot into Windows, so I used my Snow Leopard install disk to attempt a repair. It didn't even finish. I tried a repair installation. It wouldn't install with the message "This disk cannot be modified." Disk Utility is telling me to back up and clean install. If there is a way to avoid this, what is it? And I don't have a backup; if there is no way of repairing my installation how do I back up my files? Thanks. All haste is appreciated.