Adapted from my original article How to Convert an Internal Hard Drive Into an External Harddrive.
A lot of people don’t know that an external harddrive is almost identical to the one inside your computer. The only difference is that it’s in a cheap little box known as an “external enclosure”. If you’re upgrading harddrives in your laptop or desktop, you can pull out the old hard drive and convert it into an external harddrive by following these steps.
Step 1. Take the harddrive out of the computer. Take notice of the connection side of it – you’re going to need to buy the appropriate enclosure. The most common types of connections are IDE (pictured here) and SATA. Buy the external harddrive enclosure that matches the connection type.
Step 2. Once you’ve got the external harddrive enclosure, take it out of the package. If it isn’t already disassembled, you should carefully do that now. It typically consists of the enclosure case, interface (the computer chip looking thing), a cable, and sometimes heat sinks.
Step 3. If the enclosure for your external harddrive included heat sinks, screw them into the harddrive. Make sure they’re facing the same direction. These will help keep your external harddrive from overheating.
Step 4. Plug the hard drive into the interface. If it’s SATA, this will be super easy. If you’re working with IDE, be very careful not to bend the pins. Depending on the size of the drive, some of the connections may go unused. It depends on whether or not the external harddrive is big enough to require a power source.
Step 5. Place the drive into the case. Some cases are built with a two part design (like the one here) while others use a slide-in design. Once the case is assembled, screen in the remaining screws to seal the external harddrive off.
Step 6. Almost all external harddrives plug in from the outside using USB or firewire. From here, all you have to do is plug the cable from the external harddrive to your computer. The hard drive will mount on the computer just like a store bought external harddrive.
Additional Tip: You may need to format the external harddrive after you plug it in for the first time.