Wednesday, July 31, 2013

Windows 8: PS/2 keyboard and mouse are not working

Last night I've recovered an old KVM switch that I had in a box. I wanted to connect my brand new MacBook Pro to my keyboard and mouse that I'm already using to control my desktop PC. When both pc's are on I generally use a software KM switch named ShareMouse. But when the desktop PC is off i need a way to rapidly switch the keyboard and mouse to control the MacBook which is also connected to second 27 inch screen.

So, I've connected the KVM switch to MacBook using an PS/2toUSB adapter and all went fine. Then I decided to switch on desktop PC that is running Microsoft Windows 8 in order to check that everything works as expected... but I found a bad surprise. The KVM switch is very old and has only PS/2 connectors so I've connected it to the standard PS/2 ports of my motherboard but Windows 8 was not recognizing it. So I've rebooted and entered to BIOS management just to see if the KVM switch was the problem. But in the BIOS the keyboard functioned perfectly.

Well, the problem was Windows ( ah! ) and I discovered, thanks to this answer in the Microsoft Community, that Windows 8 disables the PS/2 keyboards and mouse (or simply the ports) when only a USB keyboard is connected.

In order to get things restored, you have to manually edit the registry changing a key (obviously using another keyboard and mouse!! :) ) in order to re-enable the PS/2 ports service.

The key to edit is "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt" and the value of the property "StartValue" must be set to "1" (hex). Once done, connect your PS/2 stuff and reboot and all should work properly.

Hope this help.


  1. Thanks man, it helped me! my kvm switch ps2 it's working fine on Windows 8 now.

  2. where is "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt" located? I cannot find it.

    1. hi, you have to use the registry editor. On Windows 8 just pres the Windows key + R and write "regedit" (without the double-quotes) and hit Enter. Using the registry editor, browse the registry keys to locate "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt" key. Hope this help.