ClassFactory cannot supply requested class

Hi i get a window that opens with this message "ClassFactory cannot supply requested class", when I try to look at the "Learn About topics" in User Accounts. Having looked at my other PC that is also running Windows XP Home. What should happen is a window should open giving explanations about User Accounts, User Account Types, Switching Users etc. Does anyone know what this message means, can this annoyance be fixed. It's not really important, but i would just like to know what is causing this. Thanks.