Macbook Pro not Starting I have a MacBook Pro and from the last week I have been unable to turn the machine on properly. First it displays the Apple logo and shows this message



I've done a lot of research and tried things like starting in Safe Mode. Although the error message does not come up, it will just hang at a grey screen with a spinning progress indicator.

If anyone can help, please share.
It sometimes is difficult to diagnose startup problems due to the variety of reasons (hardware issues, disk corruption, wrong configuration etc.). Apple has a bunch of support documents related to this topic:


Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Mac OS X: Gray screen appears during startup
Mac OS X: How to start up in single-user or verbose mode
OS X: About OS X Recovery