My version of Internet Explorer has an AT&T logo in the top corner where the Windows logo should be, and it says "Microsoft Internet Explorer provided by AT&T WorldNet Service" even though I don't use AT&T. Is there anyway to get rid of that and have the Windows logo back?

Try Tweak Revisited from Joe's: http://www.jsware.net/jsware/boss.html Change the title bar in IE, and lots of other neat tweaks. First cousin to Microsoft's Tweak UI. Both are freebies.

G'day Name, the logo in the corner is probably a .bmp file in your Microsoft Internet\SignUp folder, maybe named IE38.bmp or IE22.bmp or similar, just delete it or change it and close and reopen your browser and it should be gone. And is that Microsoft Internet Explorer blah blah blah on the Title bar or the Menu bar [File, Edit, View, Favorites, Tools, Help]. If it's the Title bar then do as Ed has suggested and if it's the Menu bar there may be a Toolbar.bmp in the same place as those other .bmps for the corner, delete it or modify it.