>Is there any browser related mouse click that could run the Windows search engine? While surfing a Web page, just by using the mouse, at two occasions, this has happened. The only other application running was Windows Explorer. I was wondering what could have triggered that application to start.

Windows key + E to trigger WE.

I also found http://windows.microsoft.com/en-us/windows-vista/Keyboard-shortcuts

which doesn't list Search functionality.