Using an existing key on a new laptop with a running trial of NIS 2014

ok I bought a slightly useed laptop from a friend. I mean he had it like a week before his work gave him another laptop to use.
Laptop runs a windows 8.1 OS. No the laptop came with a trial version of NIS 2014 which my friend activated. So it is running on the laptop. I have a 3 user license of NIS 2014 of which I still have one key remaining.
So my question is can I use that key to changethe trial to a full length subscription to NIS 2014?
I know one can if they started a trial and want to keep it
But in this case the other person started the trial, so I imagine the trial is under his account. If I use my key will it make the NIS on the laptop fall under my 3 user license?