To aid you, I have put together this guide which covers *every* default extension that comes with PHP5 and tells you how to get it working on Windows, what dependencies they have and also some vital tips on how you need to arrange your php.ini file and file system to ensure a painless set-up and no messy DLL conflicts.

He lays it all out in a series of two steps - getting everything all set up to make it work (including the value for the extension_dir setting and how to change your PATH variable) and the list of extensions and the DLL files they require.