PC hardware issue- IDE hard disks

I've got a PC problem here- I figured all of you are excellent troubleshooters. I'm stumped, and this is quite a surprise because I rarely get this stuck.

I had an OLD PC set up as a server, with 2x 250gb hard drives for storage and a 40gb for windows server 2003. It was in use for ~3 years, but I recently ran out of space and decided to upgrade.

I obtained a Pentium D server and installed a 750gb SATA drive in that, along with the old 250gb and 40gb IDE drives.
The 40gb IDE & SATA drives are on the motherboard and the 250gb drives are still on the IDE card.

After plugging everything in, I reformatted the 40gb OS drive and reinstalled windows server 2003. The problem is, my two 250gb drives (with all their data) do not show up in "My Computer"

Actually, they showed up the FIRST time windows booted up after the reinstallation, but never again. I can see both drives under device manager, and the IDE card has drivers.

Why would they not show up in "My Computer"?
I really need my data back. Does anyone have suggestions? Thanks!