In this case, I meant the original 120gb hard drive. That’s the reason why I synced it and left it running with the apple OS. I had to upgrade the battery (bought some cheap ones via aliexpress) and now it works like a charm. The only issue was the first charge, it took the ipod a while to recognise the battery, so having a fire wire cable to feed it the first time should do the trick. Since then, this little grandpa is still rolling for more years, I hope!
I was also doing that but after a while, I realised that with some good headphone (I use bose 700) the quality is very similar. I dig a little on the internet and some sound experts made a coparision with 320mps and the result was pretty similar. I switched my whole library to that format keeping the really old albums (mostly really old jazz and blues) of flac. I’m not sure if it’s true that the difference is imperceptible, but now I have a ton more space.