Server keys live under [HKLM|HKCU]/Software/RealVNC/WinVNC4. Viewer keys live under HKCU/Software/RealVNC/VNCViewer4. The available options that can be set are described at http://www.realvnc.com/v4/winvnc.html and http://www.realvnc.com/v4/winvncviewer.html. Cheers, Wez @ RealVNC Ltd.