I have a RS-232 mouse and my single click acts as double click in win 7! i also checked all solutions and i tried a new PS/2 mouse but there is the same problem. i also upgraded my win7 and mother board bios and all drivers. (i have not any problem with win xp and earlier versions of Microsoft os). my hardware info: MB: G41MT-ES2L VGA: Onboard RAM: 2G DDR3 OS: Win7 Ultimate (64bit) Mouse: Genius EasyMouse (RS-232 port) i forgot to say my mouse settings are Microsoft default settings and i checked my win with last versions of Avira antivirus but there was not any badware.