Ipod empty except 3 games, what's taking up 50 GB?

160 GB, I believe 2010. 8K2424XA9ZU model MC297, 2.0.4 Mac. Used to synch happily with iTunes on 2011 iMac. Recently I was prompted to factory reset it or similar, and now it doesn't even appear in iTunes or Finder on the iMac, or the 2013 MacBook. I get "disk inserted not readable by this computer". On the face of it, appears that 3 preinstalled games/"Other" are taking up 50 GB. My second identical iPod has less than a single GB in "Other", and works perfectly (with an FM transmitter in the cars). I dare not connect the good iPod to a computer! Any ideas out there? Any advice would be greatly appreciated as the local Apple Shop (Exeter, UK) doesn't have the expertise, knowledge or Macs old enough to communicate with it. Thanks everyone!