Problem 1: How to install apache and IIS on the same host - see http://www.phpbuilder.com/mail/php-windows/2001112/0125.php
for example.
Problem 2: How to make PHP run with a different INI file ?
At the moment I am trying to do just that, to install 4.3.0 on IIS alongside 4.0.6, so as not to stop other routine develpoment work of others here.
As of now, the only sure way I know of to do this is to go to the PHP source code and override the name of the INI file, or re-define the way in which the location of the INI file is found.
Yaron Yogev