Hey guys. A friend's PC has this issue. Looks like it will start ok (with the XP logo) but then a black screen pops up saying theres a problem and to choose:

Safe mode
Last known working config
Start normally
etc

Nomatter what you chose the BSOD pops up with Unmountabe Boot Volume.

I remember I had this issue years back and fixed it without the need to reinstall anything (with something on a floppy disk maybe). Can anyone help? I know I could get the important files off it and reinstall XP but I'd prefer not to.

Thanks!