This is the FreeAgent Classic. My one is a 160GB external drive.
Step 1 – using a BLUNT object, such as a thin screwdriver, slide it along the front of the wedge.
Step 2 – Pry the case apart.
Step 3 – Lift the drive out of the case, it is just sitting in the case.
Step 4 – the USB to SATA controller is just attached by two screws.
And you are done!
The biggest surprise for me was that the drive was a SATA drive.