DooPHP requires PHP 5.1.x or newer. It works with the latest PHP 5.3 wihtout glitches. For beginners, it is recommended that you download the WAMP server which packaged Apache, PHP, MySQL altogether.
If you are using Apache web server and wanted to have clean URLs without 'index.php', you would've to enable Mod_rewrite.
To use the database ORM in DooPHP, you have to enable PDO extension.
And now you are good to go!