When installing PHP 5.3 on IIS by following the manual installation steps described here (http://www.php.net/manual/en/install.windows.iis6.php) and here (http://www.php.net/manual/en/install.windows.iis7.php) it is possible to get the following error from FastCGI:
HTTP Error 500.0 - Internal Server Error
Error code: 0x800736b1
The reason this error happens is because PHP 5.3 is built by using Visual C++ 2008 compiler (VC9) and hence requires Visual C++ 2008 runtime to be installed on the machine. This error does not happen when PHP 5.3 is installed by Web Platform Installer or if you already have URL Rewrite module installed.
To fix the error download and install Visual C++ 2008 runtime from here:
(Make sure to use x86 version even if you have x64 environment)