Setup UltraVNC Repeater machine:
Install UltraVNC on your UltraVNC Repeater machine:
In the properties of the server icon in the system tray, be sure to check on the Allow Loopback Connections option (see above graphic).
In the directory where you installed UltraVNC, you will find vnc_repeater.exe.
On your UltraVNC Repeater machine, start the repeater program by running at a command prompt: "(path)\vnc_repeater.exe" 5901
Configure public router:
On your router, forward port 5901 to your UltraVNC Repeater machine.
ON REMOTE MACHINE:
UltraVNC Viewer
Now run VNCViewer.exe:
Enter the local IP address (or DNS name) of the machine you want to control.
Check on the Proxy Repeater check box, and enter the public address assigned to your UltraVNC Repeater (or router from which you are forwarding port 5901).
Press the Options... button to specify your connection options. I've found the best remote control settings to be checking on the Use 8-bit color and specify Hextile encoding method.