index.php not openingby default

Hi the list,
I’ve installed WP 2.5 on the server and have a problem. wordpress won’t navigate to index.php without addressing the page explicitly. For instance , to get to the “about” page, wordpress offers this link: https://arikiev.com/wordpress/?page_id=2

which doesnt work, but if I manually type “index.php” in front of the question mark, the page opens. Is there some setting in WP, or would there be a server control panel setting to address this? I’m stumped.