please contact Customer Support. The easiest and fastest way is the free Online Chat: www.norton.com/chat They can solve any activation / licensing problems in seconds. :)
<< I have done this in the past with no problems, the only factor was that it would expire starting when I installed the first license. >>
That is still the case -- did you install the other two more than 366 days ago and then renew either by going online to the Norton website and buying a renewal or by installing a new KEY from another package?
Did your son's laptop have this same Norton on it before he came home or some other brand of security application (or none)?
If he had the same Norton then all you may have to do is to start up his laptop, open the main screen to Norton and click on Support / Subscription Status. If you were out of step on renewals that should sunchronize him on the new expiry date which as you say runs from the date of the very first activation of any of the three.
Would you mind telling us where you purchased NAV 2010 from? Since it was a 3 license package and from 2010 would indicate it wasn't bought at the Symantec eStore. Was this other site a reputable site?