You are hereDismantle the Archos 605 / Battery Removal / Battery Pullout
Battery Pullout
With the plates out of the way the unit will be more flexible. Put down the screwdriver and use your hands now.
Lift off the cellophane attached to the battery. If you are planning to replace the battery, keep the cellophane safe and stick it back. This is important as the cellophane prevents board components from shorting to the metallic HDD that sits on top.
Now slide the battery out gently pushing the circuit downwards. The circuit is still affixed on one end, but the other end will move when pushed gently. See the orange arrows below.
Keep an eye on the battery wires soldered to the circuit board. This will require patience to do. You must slide the battery out of its housing (about 3mm). The end result will look like:
This is the battery housing:
So if one was to replace the processor and keyboard could the hard drive be upgraded and your own software installed on this device?
That's an interesting question, though it sounds a bit naive. I believe that the answer to that is that AFAIK the hard drive is not tied to the processor or to any other hardware. All hardware is tied to the software and it is the software that decides to enable, disable or reject stuff. So if you flash the processor with "your own software" then everything would work provided your software was funky enough and you would not need to change any hardware!