How can I diagnose which part needs replacement?
Typical problem, iPod gives a sad face and clicking sounds after startup. I also tried to test the hd in diagnose mode, but I can only choose between hdspecs and smart data on the menu. Hdspecs gives no serial number, temperature readout of around -90k and a hd size of 96gb, even if no hd is pluged in (same with hd inside)! When I also disconnect the hd cable, then all stays the same except temp is back to 0.
Thomas, the clicking and the fact that you can not check the HDD in diagnostics strongly suggest that your HDD is in need of replacement. Also, change the cable when you change the HDD. It is not uncommon for the cable to have some internal fractures. If you really want to check your drive, get a Zif-to-USB adapter and connect the drive to your computer via such a cable. If your drive is okay it will be fully accessible to you, and you could reformat etc. The instructions for your iPod are here iPod 5th Generation (Video) Repair Hope this helps, good luck.