If you want to replace the standard Microsoft search sites, in the search bar, with one of your preferred, such as Google, it is possible. What you need to do is edit the Localized.rsrc file in the "Internet Explorer.app -> Contents -> Resources -> English.lprog" folder (control-click on the app and pick "Show package contents"); if you are not using English, then you should open up the appropriate directory for your language. Don't forget to make a backup copy of the file!
Now with a copy of QuickConvert, flip the resource and the data forks. Next, open the file in ResEdit, open STR# resource 1000 (it has the name "Shared Strings" ). Now edit entry 470 and change it to http://www.google.com/ie.
While you are at it you can edit entry 344 to take the value http://www.google.com/search?q=%s . This will enable you to use Google for your address bar keyword searches.
Save the file, run QuickConvert on the file, to reflip the forks and the start up Internet Explorer. Now your search bar should be showing the Google search page.
[Editor's note: I have not tried this one, and I'm not likely to as I don't use IE. If you get this modification working, let us know...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020205015242964