New laptop - how do I unregister my licence on my old one?

Hi I just got a new laptop and wanting to unregister my old computer from it's Cross serial number and use that with my new laptop
I had a look around the manual and did a search but can't seem to find how to do it (sorry if its very obvious)
Hope somebody can help thanks
I had a look around the manual and did a search but can't seem to find how to do it (sorry if its very obvious)
Hope somebody can help thanks