Via a post from digg.com today, there's a pointer to an extensive guide for installing PHP 5.x on a Windows machine (Server 2003) running the IIS 6 webserver.

If you have already done basic configuration of IIS6 on Windows Server 2003, and have an otherwise functional setup, then exactly following these steps should give you a fully-functioning installation of PHP. However, since I cannot know the combination of hardware and software you are running, or any of the environment factors within which you work, I cannot gaurantee that these steps will work for you. They have worked for me and others who have followed them.

There are five parts to the guide - Installation, Configuration of PHP, Configuration of IIS, Testing, and Troubleshooting. Each step is very descriptive and provides a "sub-list" of things to be sure to set up. The troubleshooting section can help out a great deal as well, providing easy answers to common questions about the setup process...