Unable to install Joomla to root

I have previously had an alterpages site in the root directory, when I went to replace it with a joomla 3 site, It gave an error saying there is already something installed in root. I have then gone and removed the alterpages application through the control panel, once again i'm faced with the error refusing to install Joomla 3 to the root directory, I also have PHPBB forums installed as a subdirectory to root which i#d like to keep. how may I install Joomla 3 to the root directory while keeping this forum?

[karl94]

You can't using the AlterVista control panel. You can however install it in a subdirectory and then use mod_rewrite to make it look like it was installed in the root, or install it manually.