Voice Mail vs Zone Alarm

I now have Windows XP Prof as my operating system and I
am using Zone Alarm for my firewall. I have used ZA for
some time now and I am pleased with it. My problem is
that I am unable to use voice/video conversation w/the ZA
firewall. My question is, if I remove ZA firewall and use
the one that comes with XP will my system still be
secure? Under the Microsoft Messegener site it explains
how I can change ports on the firewall but I really don't
understand what they are explaining to do, so removing
the firewall will work better for me. If there is any
body out there that understands me please reply asap I
really want to use the voice conversation..........Thanks
..