You should now see the Change Search Defaults dialog, overlaying your browser window. A list of currently installed search providers is shown, with the default depicted in parentheses. In the example above, four providers are installed and Live Search is currently the default selection. To make another provider the default, first select the name so it becomes highlighted. Next, click on the button labeled Set Default.
Also, if you would like to remove a search provider from from IE8's Instant Search, select it from the list and click on the button labeled Remove.