[stomachmonkey]

First relax a bit.

Sounds like an OS problem or hardware issue unrelated to the drive.

Can you boot a PC into operational mode from an external drive or System install CD? (works on the "other" platform so I assume it works on Windows)

I would try

disconnect the internal drive

load a fresh system on the external drive and see what happens

if problen persists I'd think hardware failure or corrupt BIOS.

If everything is cool then reconnect the internal, boot from the external, run any and all virus detection programs on it and then see if you can back up individual files from the internal.

Scott