MacBook Pro hangs with progress bar midway on start up

My 17in MacBook Pro Model A1297 with OS X Yosemite, hangs on restart midway on the progress bar with Apple logo.

I have not restarted this laptop in a while and whenever I did it in the past the laptop would start after the while about 2 minutes on the progress bar.

I checked the apple online hardware diagnose and the extended memory diagnose and everything checked okay.

Also I have not backed up everything on this laptop. My son had started the Utilities(which I forgot how to) and the drive checked out good too.

Help....