Downgrading Internet Explorer from 9 to 8 is a feature “hidden” from view in Windows 7. Since there isn’t a download available for Internet Explorer 8 in Windows 7, the only way to revert back is through the “View Installed Updates” menu inside Control Panel -> Programs.
I had to revert back to IE8 since we still have a number of users with Windows XP (which only runs in IE8)
You can remove IE9 and install IE8 using the following steps.
1. Close all programs.
2. Click Start, and then click Control Panel.
3. Click Uninstall a Program under the Programs category
4. In the Tasks pane, click View installed updates.
5. In the list of installed updates, double-click Windows Internet Explorer 9.
Once Internet Explorer 9 has been uninstalled from your system, the computer will require a reboot. After rebooting, your computer should now revert back to Internet Explorer 8.
To disable IE8 or IE9 in Windows 7, go to Control Panel -> Programs. Click on the “Turn on Windows Features on or off” link. Uncheck Internet Explorer 9 (or Internet Explorer 8). The system will then act as if Internet Explorer is no longer installed. You can re-enable it via a simple checkbox.