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.

If you have Torx bits/drivers, use them. They will work much better than the flatheads.