Install disk can't repair

My Blackbook just ground to a halt this afternoon. I had to hold power button to turn it off. When I restarted it, I got a gray "no" sign (like the ghostbuster logo) where the apple should be.
So I booted to the Snow Leopard install disk to repair my boot disk. The name of the volume came up and I tried to repair it and it stopped half way through and said it can not repair the volume. It said to backup as many files possible, reformat and restore backed-up files.
How do I get to those. How can I back them up if I can't boot, or even go into Target Mode on my iMac? Is there something better than the Install disk to try and repair it?
If I choose to re-install SL will it leave my user account info intact?
Is there any hope? Is this an issue an Apple Store GB might be able to help with?

Thanks