I have an HP with dual boot, Windows (don't remember which number since I never got to that side and Redhat Linux 7.2. I tried to boot, and got the error message:

EXT3-fs: unable to read superblock
mount: error 22 mounting ext3
pivotrootivot_root(/sysroot,/sysroot./initrd) failed: 2
Freeing unused kernel memory: 220kfreed
Kernel panic: No init found Try passing init= option to kernel

I tried a number of things, including booting from floppy. Even tried booting
Windows, but the computer hung with no error message. I finally tried booting from a rescue disk, with the RedHat CD and did linux rescue. Ultimately I was told that I had no Linux partition. Very disturbing news indeed.

Anybody know what happened?

If you haven't done any serious tinkering with your computer just prior to this, then I'd say that you are experiencing a hard disc breakdown.

Good thing that you always make frequent backups to a different media.

Martin