iMac shuts down during booting
After installing the latest update of Yosemite on my iMac, when I start up I get a grey screen with the Apple logo and the progress bar. But the bar boots up half way stops and then the computer shuts down. Is there something I could do to complete the boot up?
iMac (21.5-inch Late 2009), OS X Yosemite (10.10.3)