Stop ActiveSync from asking Partnership selection

One of the annoying things about ActiveSync is that it asks for Partnership (Standard or Guest) to be selected when a connection is established, for e.g. on new devices. If you are a developer and are continously establishing Activesync connection with a device, it can be very annoying to close the selection screen every time.

Solution is to add a registry value, GuestOnly under [HKLM\Software\Microsoft\Windows CE Services]. and set its value to 0x01. This will force Guest as the selected partnership mode.
Once the device syncs in Guest mode, it will always do so.