I have successfully installed zangweb alonside IIS on a Windows XP
machine.

They will not conflict unless they both start at the same time and try
to grab port 80.

To make them play together, I shutdown and disabled the IIS service
(you might be able to simply set it to manual, but I'm not sure if the
IIS Admin service will try to start it). Then I installed zangweb and
set its services to "Manual". Now when I reboot I get no web server
until I start one.

I get no conflicts as long as I don't try starting one on top of the
other.