Its important that you choose the right version of PHP to install with Apache. There are multiple versions of the windows binaries, and it can be hard to chose the one that is right for you.
RC9 vs RC6
If you are using ISS, then you can use the RC9 version. But if you are using Apache, you should use the RC6 version.
Keep an eye on the instructions found on the Download page, as these may be more up-to-date then this Article.
Non Thread Safe vs Thread Safe
The difference between the Thread Safe and the Non Thread Safe, is that the Thread Safe runs as an Apache module, while the Non Thread Safe runs as a CGI.
If you want to run PHP as an Apache module, then choose the thread safe version. For ISS chose the Non Thread Safe.