Here it is. The standard 20GB HDD for the Xbox 360.

Notice the proprietary adapter. Inside is just a pretty standard 2.5" SATA drive...

I took these pictures as I was putting it back together, hence the Microsoft warranty sticker looking a little funny.

You may also notice the screw in the bottom left is partly out. This is because as I was replacing the screw before it, I broke my bit. I was using a 1/16" flathead bit (I don't have a T6 Torx) and used just a little too much torque and it snapped. I found another 1/16" bit to finish, but didn't get a pic.

It only voids the warranty for the drive, not the console, being as their warranties are separate.

Proceed to remove the four T6 Torx screws.

Holding the drive top up, gently pull the top half up from the bottom half. The back will rotate up as the front is connected by two plastic clips.

These clips are most easily undone by rotating the top enclosure to about 30º then lifting it up firmly.

Remove the four T10 Torx screws.

Slide the cover towards the back of the enclosure and remove. There is a small dot of lock-tite on each screw, fyi.

The third image is unnecessary, but if you quickly mouse over the second and third images it kinda makes it look animated.

Here are the innards in all their glory.

The four screws that held the cover on also held the drive in place, so just pull off the SATA connector and the drive is almost free.

To actually get the drive out, you must bend the back of the plastic part of the bottom enclosure down a little bit. Doing so shouldn't break anything, just don't go overboard and bend it excessively.

All the parts disassembled. The adapter cable will probably come out as it doesn't seem to be attached directly, but removing it would have required bending the metal enclosure and I didn't want to mess with that.

I thought it interesting to note that the drive runs at 5V 0.62A when the enclosure states 5V 1A. I wonder where the other 380mA are going.

Also interesting to note: this is a Seagate drive, while the 250GB drive upgrade I mention in the description requires a WD drive. If I understood correctly, this is because the software to format the drive to be recognized by your 360 is written for the WD firmware.