Presentation and Question

Hello,

I am new in the forum, my name is Pep Ferrer from Spain.
My question is the following one, I have two OS in my PC, XP and Vista, In order to be able to work in both sitemas I must activate software twice?

As I have an astronomical observatory, also I have another PC, I can also install the PO4?

Best regards, and thaks for the aid.

Pep Ferrer