I have a hard drive case from Ultra and added the hard drive of my choice so that it can be swapped out if desired. Plus the case is easy to replace if it fails.
The case has a tiny fan and instructions on formatting the new HD. This took a fairly long time to do for a 300 GB HD, but it only needs to be done once at the beginning. It works perfectly and is easily recognized by different computers, but it does take a very brief time to boot up when it's first plugged into the USB and powered on. The time depends on the amount of data being stored on it.