I just connected the iPod 5Gen with the 160GB HDD installed to an iMac - and no difference to connecting it to my WIN XP PC: The drive spins up - the apple logo appears and then the "sad iPod symbol" appears. The ipod does not show up in the disk utility (it does when I install the 60GB drive).

There is no way to access the disk of the iPod.

So I figure the 160GB HDD is broken - am I right?

@osxscene - let me set this straight again - I've already installed a 120GB HDD in my 5.0Gen iPod - and the iPod worked fine with it. I had a 5.0 iPod with a 120GB HDD fully working. The differences to the iPod classic with 120GB were it's outer shell and the iPod video operating system. With the 120 GB I was able to carry around loads more of videos, podcasts and of course music - so why not upgrading?

I say the iPods 5.0 - 5.5 and the iPod classic all share pretty much the same logic board and the same over all hardware. The major differences are only in the outer shells, the appearance of the software (coverflow etc.) and the disk sizes. Nothing more - interchanging the different hdds works if you have the right connecting ribbon cable at hands - and of course if the hdd you're planning to install isn't broken ;)