I have just installed Norton 360 on my new laptop, having had it previously on my old home PC and netbook. I have registered it under my email address, as I have done for all other Norton products. BUT when I try to run backup on the laptop, it scans for Norton accounts, and brings up my wife's email address, saying "we have fond your account". When I try to change the email address to mine, it says setting up backup cannot be done because the product was preivously registered to someone else. This is completely infuriating, especially as a) I have just registered this product to my own email address and Norton account and b) my wife does not have a Norton account!
If you do not get an answer here with a specific solution I'd suggest you contact the Norton OnLine Customer Support via the CHAT link as below since they have the tools and access to the databases that keep track of all this.
It seems like the N360 on your Computer and the Norton360 on your Wife's Computer were registered under different accounts. (Which means you both have purchased the same product separately and registered under your respective email address)
You are getting the message because the Product on your wife's computer is under her email, so the Backup also falls under the same email. And in your Computer the Product and the backup are under your email. A Product can be registered under only one email address and automatically the backup falls under the same email address.