If you have an Apple Store, you should make an appointment at the genius Bar to have it evaluated (FREE). You are still under warranty, so whatever is wrong will be covered (except if it has been run over by a Truck).
The suggestions we could provide all would require a working Mac OS X, which you do not have. You need Hands-on help.
the start-up music still plays.
The POST for the hardware checks out then.
I turn on my computer and all i get is a blank white/grey screen. No logo, no loading symbol, just a blank screen;
Command+R does nothing,
Holding Shift does nothing
Press and hold the power button down to turn of the machine.
Press and hold the Command Option R keys on the built in keyboard and press the power button, you have to be near your high speed Internet connection.
If you get something like "Install OS X" do that, it will overwrite your old copy with a new one and not touch your files or most programs.
If you can't install OS X, head to Disk Utility and First Aid > Repair Disk and Permissions and try reisntalling OS X again. (do not erase the drive as this will wipe your data off, unless your sure)
If you still get the white/gray screen with nothing while holding the Command Option R keys at boot time, I suspect your EFI firmware has been borked somehow and it's not loading to respond to the at boot key commands.
We are able to reinstall the EFI firmware ourselves, but the current method requires a machine with a internal optical drive. This problem occurs so rarely that it's not been used much and certainly unknown how well it works off a USB thumb drive, which is what I suspect the Apple Store/Repair will do.
Since your under warranty, I would have Apple replace the EFI firmware and check the machine out for hardware issues as well.
Buy AppleCare and a external drive for TimeMachine backups.
So I took it to the apple store, and we tried every resolution that should have resolved the problem. Our last resort was command+R. But even that did not work. Apparently my hard drive somehow was missing. I do not know how it happened, even the person helping me was astonished. So they are just going to replace it for free because it is still under warranty. If not it would have cost me over $600
Hey just a quick one
I have a 15 inch Macbook Pro (without retina) and all that happens with mine is that it starts with the music and the drive sound and then the logo and an intalling circle below it and then it goes grey or white ... Really need to know what to do ???? My Mac is my life ..... Please help ASAP ....
You have a 15" MacBook Pro 6,2 (2010 model) AND
You are running Mac OS X 10.8
There are a small number of these Macs that have a latent defect that was only uncovered by running 10.8. There is a specific diagnostic for EXACTLY this problem, and they can run it for you at any Apple Authorized Service Provider, but an Apple Store is preferable.
The program is described in this article, which you must PRINT and take the paper with you, as a hedge against "we never heard of this."