I declined to install the toolbar during an 'update' notification one day after installing McAfee, but it installed the toolbar anyway.
The same thing happened to my colleague. This sort of behaviour is typical of spyware/malware etc.
Another colleague accepted the update thinking they were being good by accepting all virus checker updates (to keep their system free from attack). They then had no clue where this mystery toolbar had appeared from, and thought they had spyware on their system.
Why would anyone expect a virus checker/firewall update to install a toolbar in any case?
Thanks Vinrod_r2, I tried the removal instructions you suggested but the option "Enable Secure Search Box" is not present at all. All the other options in the screenshot are present, but not that one.
I'm very unhappy with McAfee for foisting this toolbar on me. I specifically deselected all the options during the SiteAdvisor upgrade and it installed it anyway. Now I have no option to deselect it via the settings that should allow me to.
I have disabled the toolbar via Manage Add-Ons (IE7), although I have now lost SiteAdvisor too.