I need the Response Code to activate CS4

I'm reinstalling Adobe CS4 Design Standard on my pc. It was purchased as an upgrade from CS1 and the activation procedure shows me a Challenge Code which I'm supposed to give to Adobe in order to get a Response Code for finalizing the activation.

I used to do this on the phone, then they switched the procedure to the chat system, and now this forum.

How does it work?

Thank you,

Guido