Hi guys.
Lets say you have 3 ipods.
Lets name them 1,2 and 3.
If 1 is connected and you are working in iTunes, and now now when u connect iPod 2 , all the songs in ipod 2 will be erased and updated with the songs in the library of ipod 1.
to avoid this,
just have more than 1 account (in XP) and in each account u should connect ony one ipod.

Actually this is not true at all unless you are using an ancient version of iTunes. iTunes is able to differentiate different iPods and store separate sync settings for each iPod. You do not need multiple users, just plug in your iPod into your computer. The only way the iPod is erased is if you do a restore or you attempt to sync your iPod with another computer. Music and videos in each iPod can only be synced with one computer, however each computer can be synced with as many iPods as you wish.