Reinstall NAV 2012 after factory reset

I recently renewed my NAV 2011 through 2014, then upgraded to NAV 2012. Unfortunately my poor little laptop needs a factory reset, so how do I install 2012 again after the reset? Do I download the trial version then use my product key to fully activate it, or is there a specific download for this sort of thing? Thanks for any help :smileyhappy: