You might also consider reading Happy New Year or The Family Truckster: Part Deux.
Upgrading the AppleTV

Just wanted to post some links here that I used to upgrade the harddrive in our AppleTV from the 40GB it came with to a 100GB drive. There are many how-to guides available to walk through the process, but none of them were able to keep me from ripping the rubber mat that makes up the bottom of the box. And a big thank you goes out to my brother who aided my cause with a late-night meeting where he gave me his Torx screwdriver set that I needed. I never start these projects early enough…
As I prepared to go to bed for the night, letting the dd disk copy do its thing on the whole 37GB of the useable disk (of which only about 1.4GB was actually information) I stumbled upon this page showing a faster route by which only the first 3 partitions are copied over, saving a ton of time. So instead of this torn apart machine on the dining room table for the next couple of days, I was able to get the transfer done before it got terribly late. Really there is no difference in the directions as far as the outcome (other than the time savings) because either way you are recreating the Media partition.
And now we have about twice the space on our AppleTV. Time will tell if there are any adverse effects to the switch, but I feel good about switching in a 4200RPM drive instead of the faster and hotter 5400RPM drives some have tried.
UPDATE: I’m just guessing here, but I really think that a person could just copy over the EFI and the backup OS partitions and not worry about the other two main partitions’ data. The partitions would probably need to be created, but you could do that in much the same way as you create the expanded Media partition. I think the outcome would be that the machine would do a factory restore, which is what I ended up having to do anyway after I mistakenly selected the “streaming only” option in the initial setup. I’m quite sure it redoes (maybe even fixes the partitions?) of the OSBoot and Media partitions during that time. If I had more time, I would check that out because it would cut the time to do this upgrade down by half or more.