I just purchaed Mountaion Lion, but I can't install it. The installer keeps saying "This disk cannot be used to startup your computer" even though I am using that disk right now . I read on other sites about the same issue when installing 10.7 Lion, and how it may help to make the partition smaller, however I seem to have no recovery drive, Command+R at startup does nothing and when holding Option I just see Macintosh HD. I checked to see if my MacBook is supported and it is. Can somone please help me, I'm stuck!