Unmountable Boot Volume blue screen... caught in a loop...

Hello,

I have a windows 7 sony vaio laptop. I am unable to boot into safe mode or any of the options, cannot repair. Tried to boot off windows 7 cd, no joy. Bought external cd drive, it goes to load the boot disk but then drops back to the hard drive and does nothing. Cannot get to cmd prompt, cannot run repair, cannot reinstall. Nada! Is there anything else I could try?

Mel