The Internet Explorer argument stems from a case small-time browser company Opera filed suit against Microsoft last fall, when it charged that left alone, Internet Explorer will establish "a separate Web." Regulators will also argue that Microsoft should allow documents created in its Office applications to run as effectively on applications sold by other vendors.

Given how Microsoft's last antitrust case went down in Europe, with courts ruling against Microsoft's software bundling practices, there's a good chance the regulators will bloody up the Blue Monster again.