activate permitions

Hello

1. How many activations I am permit if I have CS4 Design Premium(box/cd). I read somewhere I have 2? Is that correct? And if so...would I be able to Install it on a new computer without deactivate the old one?
2. If I need to deactivate - Once I do that on my old XP will I be able to activate it again if the installation on WIN7 wont work?

Thank you