Problem with installation

Hello, and I'm sorry if this is the wrong place to ask - I've looked through the troubleshooting wiki and couldn't find anything that applies.

I'm having a problemwith installing elgg 1.5.

My server is a shared host using Linux, MySQL 5, and PHP 5.2.10.

Here's the problem: I have the database details entered.  When elgg asks for site details (site name, url, folders, etc.) and I click submit, I get a 404 error.  I suspect this is because the url that the submit button points at is written "/action/systemsettings/install" instead of "/action/systemsettings/install.php", but I can't determine which included file generates that button so I can't test out my thorey.

I would greatly appreciate any help anyone has to offer.  Thanks!