I had a similar problem, where my other half had a computer on which she had downloaded quite a lot of music for use on a non iPod type MP3 player.
That MP3 player packed up and she ended up with a new iPod, which was in MAC mode and had to be formatted to use on Windows.
Formatting, or "restoring" the iPod from the MAC version to Windows version will definitiely delete all music files, and any other files that have been uploaded to it.
We had problems trying to transfer some of the "protected" music files, to the iPod even though we had purchased the music legally and had the licences.
One workaround we found, was to burn the music to CD, then use the Import function into iTunes. You could try this from the MAC, onto CD, then use the CD to Import onto the PC formatted iPod. ( Quite a lengthy process if you have a LOT of music to transfer with each CD holding around 18 tracks ).
While this should technically work, you would still have to consider the copyrite issue - I do not condone any illegal sharing of music in any form.
There are alternatives you can try - there may be freeware or paid software that enable you to do this ( Google searching for "Transfer MAC iPod to Windows" should help ), and while I don't use it myself, I believe you can achieve this using Real Player with the iPod plug in, which will allow the content of your MAC formatted iPod to be downloaded onto your Windows PC. You can then format the iPod to Windows and reload it - NOTE : I haven't tried this so don't know whether it will work or not but is worth investigating.
