NumLock is sent in the virtual machine every time when switching focus to the virtual machine window

Symptoms

• Num Lock is sent in the virtual machine every time when switching focus to the virtual machine window

• Whenever I press Cmd-Tab to switch back and forth between OS X and the Windows VM, two NumLock keys are sent to the Windows VM

Cause

This is a by-design behavior used for synchronization of numeric pad state between Mac and VM.

Resolution

You can change the key used for the synchronization or disable this feature executing the following commands in Terminal ( Finder > /Applications/Utilities/Terminal):

Quit Parallels Desktop before executing commands. Otherwise changes will not take affect.

• to disable the synchronization of numeric pad state:

  defaults write 'com.parallels.Parallels Desktop' 'HID Host Hook.LED Sync' -int 0
  

• to make Parallels Desktop use and send NumLock button for the synchronization:

  defaults write 'com.parallels.Parallels Desktop' 'HID Host Hook.LED Sync' -int 1
  

  Please note that Numlock is used by default.

• to make Parallels Desktop use and send ScrollLock button for the synchronization:

  defaults write 'com.parallels.Parallels Desktop' 'HID Host Hook.LED Sync' -int 2
  

• to make Parallels Desktop use and send CapsLock button for the synchronization:

  defaults write 'com.parallels.Parallels Desktop' 'HID Host Hook.LED Sync' -int 3
  

• to discard all changes, please use the following command:

  defaults delete 'com.parallels.Parallels Desktop' 'HID Host Hook.LED Sync'
  

Note the changes will be applied to all virtual machines running on the Mac.