I was not watching what I was doing and I install ML on an external HD. The computer booted with not problem. That is when I realized I had installed ML on the external HD. I thought the obvious solution would be reinstall ML on the Macintosh HD. For some reason the computer will not boot. I get a gray screen. Any ideas to help?
Have you installed Mountain Lion on the computer? You typed the computer booted with no problem, then you typed you got a grey screen.
Maybe these will help:
After I started the computer, it booted from the external HD. That was when I realized I had installed ML on the external HD. I had ML previously on the internal HD and I was reinstalling it. When I reinstalled ML, I made sure I selected the internal HD. When I returned to the computer, it had not restarted and the dialogue box for ML was not the screen. I selected continue. From that point on, all I have is a gray screen, I have tried all the key combinations to restart the computer. I have turned it off and on. All I get is the gray screen.
Try booting into the Safe Mode. Shut down the computer and then power it back up. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart. For each disable/delete, you will need to restart if you don't do them all at once.
If you still get the gray screen, try booting into the Recovery Volume (command - R), run Disk Utility Repair Permissions and Verify disc. If you want to save a step, you can try reinstalling Mountain Lion on the internal drive. Otherwise, try booting into the normal mode before reinstalling.
Thank you for the help. I resolved the issue. However, I am not sure why. I unplugged the computer for about twenty minutes. When I plugged it back in, it started.
Unable to start computer
