NIS 2012 - Convert trial to full

Hi:

 

I have been a user of NIS for a few years now. Took out a new 3 user licence for 2011 last year and 2 licences were installed on XP 32 bit machines. Both machines were recently upgraded to NIS2012

 

Just purchased a new Win 7 64 bit HP desktop which has a 60 day trial for NIS2012 preloaded.

 

Can I just enter the remaining "unused" key I already have to convert the trial to a full version on the HP or should I  uninstall and reinstall?

 

Thanks