GREY SCREEN OF DEATH

Hello. My computer froze last week. I was in the middle of minimizing a window in Safari and just before it got sucked down to the bottom of the screen, it froze. My mouse was frozen and I couldn't force quit anything, so I forced the computer to turn off by holding the power button. When I turned it back on, I couldn't pass the grey screen and the Apple logo changed from an apple to a prohibited sign (like the red circle and diagonal line you'd see on a no smoking sign). I went onto Apple's pages and after following all the former steps, I've come to the suggestion to use Disk Utility to perform a repair on the volume. The only problem is Disk Utility isn't giving me any options to do anything. Maybe there is an option, but I'm just not seeing it because I have no idea what I'm doing. Hahaha! If someone could give me some guidance, it would be really appreciated!

So I put in the disc and hold "C" on start up. Great, the disc works! I open the Disk Utilities window from the Utilities menu. The window opens and at the top of the screen, Verify, Burn, New Image, and Convert are available to click on. Everything else in the same bar is greyed out. Underneath that, there are two windows, a thin white one to the left and a big square grey one on the right. The white one has a symbol of a cd and "HL-DT-ST DVDRW GS23N" beside it. Under that there's another symbol of a cd and "Mac OS X Install DVD". In the grey square, it says, "Select a disk, volume, or image".

So, I click on the "Mac OS..." cd option in the white box and the grey square changes with First Aid, Erase, and Restore options at the top. I'm automatically put in the First Aid window. Underneath that, there's some words, and a box check-marked that says Show Details. The box under Show Details is empty. Under the empty box, the options Verify Disk Permission, Repair Disk Permission, Verify Disk, and Repair Disk are all greyed out.

So, I'm having trouble because I have absolutely no idea what to do and can't find this volume folder thing to repair...

Also, it may be a good point to say that I have information I don't want to lose, so reformatting and starting over is only a last resort!

Thanks!