As Christian Wenz points out, there's some information in this blog entry about getting PHP up and running on IIS7 (RC1) for Windows.

Thanks to some small tweaks we made in RC1, it is now easier than EVER to get PHP working on IIS.

The method basically involves grabbing the latest PHP and installing it (including the php.ini file) and installing IIS7 with the ISAPI Extension component or CGI component. Then it's just a matter of setting up the right handler mapping. He provides screenshots of the process to help show you exactly where to go.