Some wheel mice ship with default settings that do not send the standard wheel events to programs, but instead try to simulate scroll bar events. Usually this is configurable from the hardware specific pages on the mouse control panel. The middle button is often mapped in the same settings to have some functionality other than sending middle mouse button events. In some cases, uninstalling the manufacturer’s drivers and telling Windows to use the generic USB or PS/2 drivers is the only way to make the mouse work properly.