That would be your internal speaker. It sounds like maybe the wireless receiver has a buffer that's running out of room when you scroll to fast... I've never heard of it, but usually overloaded buffers are what make your internal speaker beep like that. Try switching ports. If it's USB, use a converter to plug it into a PS/2; if it's PS/2, take off the adapter and plug it directly into USB. If it's plugged into PS/2 right now, plugging into USB should fix it. If it's in USB right now... well, it's worth trying, but switching ports probably won't fix it.