Connect it to computer and run iTunes. Select iPod in the iTunes sidebar, under DEVICES. Over to the right, go to the Summary tab. There should be a Restore button.
Restore will erase the iPod, install the latest available software, and give it the default "factory" settings. If it ask if you want to sync the iPod to your computer, select cancel (or no).
When your friend connects the iPod for the first time, he can choose the option to sync the iPod to his computer.
Can you identify your iPod model using this list?
Also, do you use a Mac or Windows PC?
If the iPod does not show up under DEVICES in iTunes, how have you been loading music on it in the past?