At the risk of being incredibly patronising, have you also installed server software, such as Apache or IIS?
If you are running Apache server, you'll need to manually edit the "httpd.conf" file for PHP to work. Open it in Notepad or another editor and put the following in the script alias section (search for "ScriptAlias" without quotes to find it.)
ScriptAlias /php/ "C:/php/"
AddType application/x-httpd-php .php
Action application/x-httpd-php "/php/php.exe"
You will probably have PHP and Apache installed, but neither of them knows the other exists.
Edit: Just noticed something else that might be causing this. You are using the shortened version of the PHP tags, and these might not be enabled.
The proper (recommended) way of opening and closing PHP scripts is with:
<?
php echo("Hello World");
?>
Try that. If it works, either use it or read the PHP Manual (
www.php.net) to find out how to enable Short Tags.
