First of all, why would anyone want to take this thing apart? I personally love the design. It looks great, it's quiet, reliable, stackable, and portable. Sure, it needs an external power source, and it's becoming a bit large for today's external hard drive standards, but other than that, this thing is pretty well designed, IMO.
But for whatever reason, you want to open the enclosure up. After many exhaustive hours of research, I was surprised to find that there was absolutely no information on the web about taking this thing apart. I had imagined it to be a pretty prolific piece of hardware, but maybe I was wrong. Several people in forums told me it was impossible to take apart without breaking the enclosure, but that is simply not true. In fact, the internal design seems to even facilitate disassembly to a certain degree. Whether this was intended or not, I don't know. In any case, let's get started:
You will need:
Some sort of flat, sturdy tool like a flathead screwdriver
1 Phillips head screwdriver
1 2.4 m/m flathead screw driver OR 1 2.5 m/m Hex screwdriver OR 1 Torx screw bit
1 2.0 m/m flathead screwdriver OR 1 small Torx bit
Obviously, make sure you only work on the hard drive and enclosure while it's unplugged. Also, as is true with all computer electronics, you should try to maintain a non-static environment while working. Use proper safety precaution and go slow. If you get stuck, use the photos as references.
Finally, this WILL void your warranty.
(I apologize ahead of time for the dark photos)
Note: You might also read through the comments for additional help - there are a lot of good tips and insights which can further aid your disassembly.
Step 1: Removing the Outer Enclosure
Step 2: Removing the Inner Enclosure
1. They use special parallel Torx screws which require a special bit to unscrew. If you don't have that special bit, don't worry, you can use a 2.4 m/m flathead bit or a 2.5 m/m Hex bit instead.
2. The half of the casing closest to you isn't threaded - once the screws come out the far end, you can pull them out.
3. The two halves of the casing have a rubber grommet between each connection.
4. The plastic legs at the back of the case are longer than the front of the case. This should help you keep track of which way it goes back on. (The side panels are uneven as well)
The grommets on the legs stick a bit, so you may have to do some wiggling as you pull this part of the casing off.
Step 3: Remove the Unit From the Remaining Casing
Now, let's take a look at the sides. There are three screws total, though four holes, so your model might be different. You can take these screws out now if you want (they are normal Phillips screws) but don't try to remove these plastic sidings just yet.
What you need to do now is pull the back of the case a bit and pull up on the back of the main unit. Your power switch, USB and firewire ports should just clear the space. When you do this, be aware of the plastic legs that go up through the side plastic panels. Next, you want to slowly and carefully wiggle the front of the unit out. Once the unit is free of the other half of the outermost casing, you'll see why you didn't take off the plastic side panels yet. You will now have access to the hidden screws that you couldn't reach before. Go ahead and take out all these screws, and peel off these plastic side panels. They are adhesive, but not so much that any force will be required.
Step 4: Remove the Drive From the Board
IMPORTANT: Be careful as you pull the hard drive from the shielding as the power plug is still connected and wired. If you pull hard or jerk the drive, you may very well rip the cables out, which would make the enclosure useless for future use. Don't worry about the IDE connection - it's solid, not cabled.
Once you have the hard drive out, don't forget to put those two Torx screws back in.
Step 5: Utilize the Hard Drive
EDIT: A good point has been brought up in the comments - if you do decide to put a different drive in the leftover enclosure when you're finished, be aware that you may run into compatibility issues. Besides the fact that the power source in the enclosure probably won't be sufficient to run higher capacity/rpm drives, you may run into problems with the board recognizing the drive, etc.