Pit it's a module that plugs on the back of the drive. One drive, one module. You have to be careful when buying them. You can get confused as to what variation you need.
Now to the OP. Most motherboards are moving away from the old school IDE for SATA. It's simpler to make and it's a whole lot fast in the data transfer.
However you can add a goody that won't break the bank or confuse the dickens out of ya when you try to order one and that is this little jewel: http://www.geeks.com/details.asp?invtid=A-142
I have one of those and it's been purring along for over 4 years now and has not missed a beat or screwed up in any way. For XP and Vista you just plug it in, plug in your IDE drives and reboot.
There are 2 flavors of that card. One will do optical drives and hard drives and the other does hard drives only. The hard drive only is the most popular so you don't have to worry about getting the wrong one.
And for what they do they are very inexpensive. If memory serves, I think I gave under 50 dollars for it.