Windows Media Player does not display all the songs on my iPod
If Windows Media Player does not display all the songs that are shown in the iPod menu, please read the notes below:
You synced songs using iTunes, or you used a different computer to sync your iPod
If you use a different application such as iTunes to modify the music library on the iPod, or you sync your iPod using a different computer, the changes may not be immediately seen in Windows Media Player.
This behavior is by design. Windows Media Player caches the music library on your iPod, i.e. it does not download the entire library every time you connect your iPod in order to save time. To force Windows Media Player to refresh the music library from your iPod, click the Sync tab and then Refresh.