Installing NIS 2011 on new computer after replacing old computer

Presently  with a 3 user version of NIS 2011, I will soon be replacing an old desktop computer that is one of the 3 having most of a year of coverage remaining. I have the disc with key, so what I want to know is how to I uninstall the copy from my old desktop computer so my subscription shows 2 computers again so the 3rd computer will be the new one?

 

I will only have NIS 2011 on 3 computers once I remove the copy from the old first, but from what I've seen, if the correct steps are not taken, the process will not allow the program to work properly.

 

Thanks!