Did you know Microsoft and PHP have came out faster PHP with IIS named wincache(Windows Cache Extension) last week?
This means that you will no longer see PHP process keep used up your memory if you are using IIS Web Services anymore.
How to get wincache? It is very easy, make sure that you have PHP5.2 or PHP5.3 installed with your machine. Even you may install Microsoft Web Platform Installer from your Windows Server 2003 or Windows Server 2008 machine to install it.
For more information, you may refer to the URL below for more detail.
You might ask what is the advantage with WinCache extension? IIS (Internet Information System) have listed Wincache could increase the PHP performance on Windows by caching bytecode in memory, reduce file system I/O used in memory, etc.