Boot Device

[Yikes!]

My husband is not impressed. I booted Knoppix in his pc to show him the application and when we re-botted his pc we receive a message Unmountable_Boot_Device. His pc was configuered with c, d, and m drives. When I re-boot with knoppix, we can see hda1 and hda2 which are the d and m paritioned drives but i cannot get to c anymore.

Any ideas anyone?

And of course, I need data of of c...this is not good...
Thanks and I appreciate any expertise and assistance anyone may be able to provide....
Yikes!