VNC Server on Windows Vista

After installing VNC (Server) on a Vista machine in service mode, I was unable to connect to it on the local LAN via a wifi-connected Vista laptop. VNC Viewer would give me a "connection closed unexpectedly" error. Both machines had the Vista firewall disabled. The event viewer on the machine running VNC Server had the following entry:

Unable to connect session to Console: Access is denied.

The failure is due to security restrictions of Session 0 in Windows Vista. For more on Session 0 see here.

The workaround is to run VNC Server not as a service, but in User mode instead. You can add the shortcut of RealVNC User mode to your startup entries to ensure it starts for every boot.

Source (My Digital Life).