While you can always set the jumpers on a hard drive you want to recover and slave it in an exsisting system, it is much easier to use a USB enclosure to connect a hard drive to your system for testing/diagnosis. When hooking directly to the system, you risk the integrity of the connections and hardware inside the case. If you are looking for a better way – go pick up a USB enclosure from a local computer store (try to find a locally owned shop) and use that instead!
If you want to order online, here are some good prices:
The only thing you need to be concered with when buying is the connection type of your hard drive. Generally they are either SATA or PATA (IDE). You need to buy the type that supports your type of hard drive.
PATA (IDE) is on the top, SATA is on the bottom.
Once you connect your disk, simply plug the USB cable into your computer to access (or attempt to access!) the data.