Our old PC finally died a slow, agonizing death. So we replaced it with a new PC, which has an S-ATA hard drive. We need to retrieve the data from the old IDE drive in the dead PC (I'm hoping that the reason it died was not due to a hard drive problem; I think it was a motherboard/CPU problem since a new drive won't boot, either). My question is, what is required to put the old IDE drive into the new PC with the S-ATA drive? Just a cable, or do I need to get some sort of card, too? Or is there some other method of getting to our old files? Thanks.

What's the make/model of the computer and/or motherboard?

SATA-capable motherboards often still include an interface/connection for IDE drives. If that's the case you'll just need to get an IDE ribbon cable, plug the drive in, and see if the BIOS detects it. If so, you should be good to go.

If the motherboard doesn't have any IDE connectors, you'll have to buy either an IDE->SATA adaptor kit or an IDE PCI controller card.

The new PC is a Dell XPS Gen4; have no idea what motherboard. I opened it up, though; there is no IDE interface, but there is one spare slot where maybe I can put one. I suppose I might even be able to try the interface card from the old PC (Gateway AMD). Thanks for your advise.

Sure- if you've got an old controller card lying around, even better. Try it; it should do the trick.