unable to boot Mac OS after installing bootcamp Installed bootcamp Win7 on my MBPro with Yosemite a couple weeks ago and both OS's worked fine for some time, until recently the Mac OS suddenly decided it couldn't boot anymore. If I select the Mac partition at startup, the computer will get stuck at the Apple logo with the progress bar making somewhere near half way through. I don't think I've done much in the Mac partition under Windows at all over this period, much less possibly modifying the system files. I can get prepared for reinstalling it at any time, but nonetheless would like to know what most likely is the cause and if it is in any way possible to repair Mac OS under Windows at all.
Try using single user mode to repair your disk: http://osxdaily.com/2013/08/07/how-to-repair-a-mac-disk-with-fsck-from-single-user-mode/