Hi brigitfromwi,
Have you sync'd this iPod with your iTunes library on that computer before? If so, then all you need to do is to:
Hook up your iPod to the computer, and when it shows up under Devices, select it
Then, to the right, under the Music Tab, uncheck the "Sync Music" option box at the top of thae Music Profile page
The Sync. That will remove all of the music from the iPod, and leave your library in tact.
If you have never sync'd with that iTunes library, then there would be other sync issues you would want to take into consideration. So, let us know which scenario you are talking about and we can go from there.
Cheers,
GB