How to get 2 cams on 2 different port 1394 ...

Hi there !
I can't solve this problem:
I want to plug 2 cams on a laptop using a PCMCIA firewire card which as 2 port on it.
When i switch on the cams, win XP recognize only one cam. In fact affect only one port automatically. If I plug another hardware instead ( a cam and a hard disk for ex) , it works as the system affect 2 differents ports 1394.
How to get XP "thinking" that I plug two different hardware and have 2 ports 1394 ?

(It worked one time for bothe cams, don't know why .... I suppose the order to start some process was important)

Thks for help
Cheers
Denis