If you want to, you can have your HDD on the same channel as your DVD drive. You will need an IDE cable with two connectors on it. These can be had at any computer store such as CompUSA.
I believe that
THIS will allow you to use your IDE drive on the SATA controller. You will also need a SATA cable.
I haven't had any problem running two external USB 2.0 hard drive enclosures. Just make sure you read some reviews before settling on one because some are better than others. The cheap one I had didn't work properly. I have two of
THESE and they work great.
THIS one did not work. Like I said, if you go this route be sure to read some reviews and follow the directions.