Last night, I plugged in another HD to back up something. The strange thing was, I had to boot in safe mode, or else windows would not get past the splash screen.

today, I replaced it w/ the 2nd HD i normally have in my computer, and now when i boot the splash screen appears, adn after a minute the computer reboots. If i boot in safe mode or last good config, it reboots after about 2 seconds. When I boot from the XP disk, it doesnt recognize the XP installation, or the type of partition. CHKDSK says "one or more unrecoverable errors", but it shows that instantly, like it isnt even checking the HD. When I boot using Partion Magic, it sees the NTFS partition w/ the system on it, and then it sees a HTFS partition that is full (I had a 2nd NTFS partion on that drive). Deleting the HTFS partion gives an error.

I dont think my HD is bad, because i run disk check weekly, and have had no problems until today.

Any ideas?