Lately when we've been switching between users on my PC (WinXP Home) the whole computer has been locking up. I have to perform a hard restart to get it to work. Today the same thing happened, but now it won't even boot up (sits on the black Windows screen with the progress bar). And it's given me the BSoD twice with "Unmountable Boot Volume".

There have been no recent hardware changes (besides a GPU about 6 months ago). Any help with what's goin on? Thanks!

Damaged HD, or corrupted bootloader, corrupted file table. You will need further diagnosis with a boot disk.

I just loaded up the recovery disk and I'm running a chkdsk right now. It's taking quite a while, however.