After moving all the songs from the hard disk C, itunes sync songs no more.
After I moved all my songs from the hard disk C to D, the itunes library was empty, so there were no more songs available, and there came the report that only one itunes can be enabled on my PC or similar. I'm still drawn songs to the library and wanted to sync, but in the end there was no song on the ipod. All songs which were previously on the iPod are exists
iPod touch