I can't install Mountain lion. It says my HD is locked

I just encountered this issue with my old early 2011 MacBook Pro... The OS indicated the drive was fine upon ' verify disk.' But, it would not boot anymore.... Then, I got into the boot with command + r option to repair the OS. Upon trying to reinstall OS X Mountain Lion got the ' disk locked' message. This told me somehow the MBR ( master boot record / equiv) was messed up; possibly bad instructions, or even more likely, hard drive going south.

So, I took someone's advice in this thread, I pulled the drive out of the laptop, hooked it up to an enclosure, connected it to my new MacBook Pro, and the OS X Yosemite tells me immediately, ' bad hard drive, cannot fix, will run, but may die soon. Back up ASAP.' So, I'm now backing up...

Thanks to this thread you all saved me a lot of time by trying to reinstall the OS, tinkering with settings and different boot modes... Instead of going any further with all that, I just yanked the drive and hooked it up to an enclosure and I'm getting my lost files back!!!! I"M HAPPY 🙂 🙂 🙂 🙂 🙂 ( and I know where to go from here...!)

THANKS!

I ran into this problem because I had no drives mounted. Go into utilities, disk utilities and check to ensure you have the drive/partition mounted that you want to use for the OS install.

having the same problem

You might want to consider starting a new discussion. Since this one is a couple of years old, less people are likely to look at it. A new post would be much more visible. You can link to this one.