If I rebuild my pc - how does NIS 2010 remeber my licence on that PC

Hi Guys,

 

I've just purchased NIS 2010 for 3 PCs

 

I've installed it on 3 of my machines, but what happens if I need to rebuild my machines, How does NIS 2010 know that I previously had it installed on a machine and that I'm not just installing it on another machine.

 

Do I have to do anything to tell it what machines I have it installed on?

 

Thanks in advance.