php not running when installing wordpress

hi everyone
newbie here.
im trying to host a website on my local machine.
I downloaded mySql, wordpress3.0.1 and php already and they are all installed.

When i follow the 5 min installation thing on the website and tried to open wp-admin/install.php; the following error message appeared:
Error: PHP is not running
WordPress requires that your web server is running PHP. Your server does not have PHP installed, or PHP is turned off.

It says php is not installed right? but when i check my system and find that Php 5 is actually installed in my machine coz i can see it from program menu.

so im stuck at the installation progress at the moment.
im first time using wordpress to host website; please help out if you can. many thanks.