If your machine came with IE9, you can't uninstall it. If your machine came with IE8 and was updated to IE9, you can: just go into Control Panel>Software and uninstall it. IE8 will be restored. But this won't change the settings at all.
To bring the settings back to what they were initally go to Tools>Internet Options>Advanced to restore the advanced settings; there might be something on other tabs also.
But my guess is none of the two will help against your problem. Then post again (with more details about your home page settings and the exact message) in our http://forums.cnet.com/computer-help-forum/
When I'm starting the IE9, it shows a warning for missing scripts and I have to answer twice I still want to run it. I need maybe to uninstall the IE9 and install it again. How to? Or maybe restore the initial settings - how to?