Arf, I guess Linux is also the recommendation from eZ Systems.
http://ez.no/ezpublish/requirements
In my opinion, I suggest you, if it is possible, to install either a linux host or a virtual machine (cheaper).
By the way, for your Apache 1.3, it will be difficult to get the sources of this version : Apache Fundation doesn't support it anymore, this is due to performance and stability issues on Windows.
Please do use Apache 2.2 on windows. It is much more stable than 1.3, and maintained too. And it has many better features/modules.
In my own experience, the php problems with multithreaded webservers are specific to a very limited set of extensions/function calls. And if you really run into one of those, you can always switch to fastcgi (useful stuff can be downloaded from apachelounge.com).
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