UNMOUNTABLE_BOOT_VOLUME, there seems to be a corrupted data and can be fix by running CHKDSK at the recovery console (most of the time)
If you can't boot any of the options as you said above, use your windows installation CD to boot. If you don't have the CD, you can download and burn this recovery console (yes, you need another PC for you to burn this one).
Once you boot your PC on CD, allow it to run until it reaches the Welcome Setup screen.
From there you can press R.
It will ask you which Windows instillation, if you have only 1, press 1
It will ask for an administrator password, if you don't have, simply press ENTER
CHKDSK C: /R
I like the /R parameter because it thoroughly checks the entire hard disk, but can take a long time.
If you want to just fix what's corrupted, you can run;
CHKDSK C: /F
By the way, I just joined here and I'm not sure if there is detailed instructions on this particular problem. Probably there is, but I not very familiar with the forum, yet. Newbie, so to speak
Edited by Computer Security, 25 May 2012 - 12:44 AM.