I've just removed two references to [[Image:Mac Internet Explorer.png]] and two to [[Image:XPlogo.png]] from user pages. While both of these images have a good argument for fair use on the appropriate articles about their related products, there is no fair use argument for placing these on user pages or in cutesy little "product endorsement" boxes (see [[User:NSR/userboxes]]) for people to put on their user pages. Wikipedia doesn't need to carry advertisements for anybody, especially not using copyrighted logos.
Kelly