When installing PHP on Windows Server, I set up a simple ECHO page to test the install. It worked fine. I tried a simple phpinfo() file, and got a 500 error. Internet Explorer was no help, and kept saying the webpage contains protected content, even after disabling UAC, adding to Trusted Site, etc.
You have to set the default time zone in your php.ini file, and then phpinfo() will work fine.
List of time zones (America): http://us.php.net/manual/en/timezones.america.php