Quoting jim scott <jimdscott at gmail.com>:

> I have a four month old SATA HD in my FC 4 system. A few days ago I
> installed an IDE HD that a friend couldn't use any more. Since then, my
> system has been very unstable. The system spontaneously reboots and leaves
> me at a boot up screen with a message saying it can't find my SATA drive.
>
> I changed the bay on my SATA drive during the install, so I checked the
> power and SATA cables. Those both looked good, but I reseated them both to
> be sure. Are there any system messages that I should look for? Any other
> potential traps when adding an IDE HD to a system? Thanks for any clues.
>

Sounds like a potential issue with the motherboard. You may want to 
check their
support site and see if there are any known issues where it flakes out due to
having an IDE and SATA drive installed. I haven't heard of this before, but I
could understand how it would happen. Maybe a bios update would resolve it.

Josh