Change product key or serial number on existing computer

long story short, i have 2 different licenses for NIS.  one was one i got years ago and kept renewing for 1 pc.  Then i decided to buy a multiuser license since i wanted to install it on multiple computers.This has a different product code and serial #.  Everything was good until i tried to renew the multiuser license from the computer i first installed it on. Somehow, it renewed the single license and then changed the product code and serial number to the single license one. 

 

So i'm now trying to change the product code and serial to the correct one (to the multi user license) but i can't.  I've tried running the Norton removal tool several times, but when i reinstall NIS, it just automatically finds the incorrect license (single user). it doesn't prompt me for a product key or anything.

 

Where is this value stored and/or how do i get rid of it or change it?? Thanks in advance!