Update: Thanks to reader Epon, we now have a way to do this without requiring iPartition. So you can now do the upgrade for only the price of your new harddrive.
Here it is, a step by step tutorial on upgrading your Apple TV harddrive. With thanks to Jonathan Bare, the brave soul who worked this out!
It should be noted that this process will almost certainly void your Apple TV’s warranty and you are attempting this upgrade at your own risk.
For more goto:
appletvhacks.net
