Got an Intellimouse mouse explorer from a friend who brought the new 3.0 version. It was working fine on his computer. I turned off my computer took out my old mouse (Ps2 MS standard). Plugged the Intelli mouse into a USB port. Turned on computer. Mouse wouldn't work. Got drivers from MS (4.1 s) installed those, same again no mouse movement. Tried different USB port same again, tried PS/2 connector same again. Ive now gone back to my MS standard wheelmouse and it works fine. I do get a Light underneth the Intelimouse so it appears to be on.