I've just got a webcam and  the person I talk to most is behind a NAT firewall, as am I. Would it increase the performance if one or both of us opened a port on our routers, if so what port would I enable?

I had a quick look on the msn help and it said you need to enable Universal Plug and Play which my router doesn't support. I'm pretty sure the other person's router supports it, so if just one of us enabled it would it make any difference.

Thanks

UPnP will only make a difference if enabled both ends. As for the ports to open, search around a bit, and you'll find which ones they are.