Motherboard won't recognize drives on IDE line,

This could be a couple of problems. you may need to check the jumper on the hard drive. If the hard drive is the only drive on that ide channel, many motherboards prefer it to be set to cable select or CS on the hard drive. If you have 2 drives on there, one needs to be master or MA, and the other needs to be set to slave or SL. If that's not the problem, try a new ide cable. then a new hard drive. after that, it's the motherboard.

Have you tried a different IDE cable and/or an IDE port? Make sure your jumpers are set right for the IDE devices. Also if possible try the drives on another computer.