'Facebook' application won't close on WinXP shutdown

I've posted about this before, but got no replies.

My WinXP (SP4) machine seens to have picked up something I can't find. At shutdown/reboot it hangs with a "can't end program" box. The program is being called 'Facebook'. Now, I don't go near Facebook and certainly didn't install it intentionally (although I wouldn't put it past things like iTunes or the BBC iPlayer to install it without telling me).

But -- there seems to be no such program on the system. Nothing in the Registry, and no file anywhere with even part of the name 'facebook'. It doesn't show up in Process Manager Explorer. But the "end program" sees it as that name.

(Oh, and the "end program", having done a countdown warning that the program is then going to be terminated, doesn't -- it just sits at another window asking if I want to end the program or 'continue' (both actually terminate it and continue the shutdown/reboot). This is really annoying...)

I'm making this public (but screening anonymous)...