How can i open for RC, Inv and Imagine in WinXP FW?

I thought when ZenAgent is installed on a XP-box, it opens for RC etc.
I can connect til Win2000 and Win98 PC and RC work like a charm, but i
really want this to work on XP.

I know there is some port to open, but this meen i have to add this change
on every computers. I there som way to make this change remotely?
What ports must be opened?

Best regard,
Ronny Simonsen
Narvik - Norway

Using Opera M2, http://www.opera.com/