You have stumbled on what is called Digital Rights Management. You can't share tunes across machines this way.
Bob
Hello,
Just got my first iPod for christmas - Yay!
I added a bunch of mp3's to the iTune library which updated the iPod, it worked pretty well. But when I installed my iPod on a second computer everything was gone, no more mp3's.
Is there anyway I could have updated iTune's library from the iPod or is iTunes a one computer software?
Also, is iPod limited to iTunes or can I use other software?

Chowhound
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