Hi I know this is a bit of an old thread, but just adding this in case its useful to anyone who comes across this by searching. I have just successfully upgraded my 5th gen 30GB ipod to 120GB. I fitted a Samsung HS12YHA 120GB disk, which you can get very cheaply on eBay. This is the model that Tony mentioned in his earlier post on this thread. It works fine and (as Tony also pointed out) - this disk is only 5mm thick so it can be fitted into the case of the 30GB 5th gen ipod without the need to replace any other parts (many other hard disks are 8mm thick so would not fit the 30GB ipod 5th gen). Just for completeness, my ipod is a 30GB Gen 5.5 (also known as 5th generation late 2006). After fitting the new hard drive iTunes recognises it as a 120GB iPod - I've copied about 90GB of music on to it and it is working fine so far.