Use of SR on more PC...

Hi All man! I'm new here and I offer my most cordial greetings. I wanted to ask you a simple question

I have Two PC with OS Windows XP-32bit (workStation) and Win7-64bit (notebook). My version of SolidRock is installed on Win7 OS but I want to use it on Windows XP (my workstation). On XP, SR have a different number of Request Code...

Question:

Can I use the same number serial?
I can transfer the license?
I do buy another license?

Waiting for your kind response, a big Ciao