MacBook can't boot - Gray screen

[sriethmiller]

I have an early 2011 MacBook Pro that is no longer under AppleCare coverage. I was downloading Yosemite last night when apps and the system itself became mostly unresponsive. I was able to force a shutdown, but now the system can't boot. I hear the startup chime and get a plain gray screen, but thats as far as it gets.

http://support.apple.com/kb/TS2570?viewlocale=en_US

I have tried everything in the above support article. The only thing is I don't know where the original RAM is, but I tried removing one stick of RAM at a time and neither one made a difference.

As I said I can't get the system to boot to a USB drive or the install disk, although the SuperDrive does spin up when I attempt to boot to it.

Without being able to boot to anything the only option I can think of is to try to replace the hard drive as I suspect the OS is corrupted.

If anyone has some thoughts or advice I would greatly welcome it, thanks!

 

[chas_m]

If anyone has some thoughts or advice I would greatly welcome it, thanks!

What happens when you boot holding command-r?

 

[dtravis7]

Also when trying to boot from the USB drive, does it contain a bootable OSX on it? What keys are you holding down to try and get it to boot from Install Media or USB drive?

 

[sriethmiller]

I've tried Command+R, nothing happens. I press and hold the Option key to choose a different boot drive, nothing happens. I try pressing and holding the C button to boot to the disk, I can hear the SuperDrive spin up, but nothing happens. Yes, I loaded OS X Yosemite onto my USB drive and used it to successfully install Yosemite on my girlfriends machine, so I know the USB stick works. Since I've checked the RAM as best I can without replacing it, I suspect (hope) its the hard drive.