Two different ipods, two different libraries, 1 computer

I have tried to do this: http://support.apple.com/kb/ht1495

But it ended up deleting the old library, and when I got back the old library, the new one was deleted. Utterly useless.

I have an itouch and the new ipod nano, and I created a new account for BOTH, however, neither could exist with the other in the same computer.

Is apple's solution that I buy a new computer? This is extremely frustrating.