OS X Mountain Lion: If you see a blue screen at startup
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If you see a blank blue screen or a blue screen with a colored pinwheel when you try to start your computer, but starting up doesn’t progress, you may have a problem with damaged or incompatible startup items or software.
Note: To print these instructions, open the Help Viewer’s Action pop-up menu (looks like a gear) and choose Print.
- If you are starting up from a DVD, it must be a disc that came with your computer or OS X retail package. Discs from other Mac models may not work with your computer.
- Restart the computer in safe mode. If the computer successfully starts up in safe mode, choose Apple menu > Restart to see whether the computer will restart normally.
- If you see the login window prompting you for a user name and password, but starting up doesn't progress, you may have incompatible login items.
- Repair your startup disk or disk permissions using Disk Utility.
Repair a disk
- Back up your disk and then reinstall OS X.
Last Modified: Sep 4, 2015