Resyncing ipod 4th gen to correct computer

I recently purchased a 4^th generation ipod touch. The device was first sync’d to my backup computer because my main computer was being repaired. When I now attempt to sync the device through iTunes in my main computer, I get a message stating that you 'can’t sync the ipod to two computers…do I want to erase the ipod and resync?'

I don’t want to erase the ipod, but I do want to resync the ipod to my main computer. How can I do this? Is it just a simple case of resyncing the device in iTunes on main computer, or do I need to do something in iTunes on my backup computer?

I’ve deauthorized the backup computer and don’t intend to use it any longer.

My iTunes is v10.6.3; my OS is 10.5.8.

Any help would be appreciated. Thanks.