I'm using UltraVNC very much. Thanks a lot!

I also had the problem that configuring the router most of the time is not feasible for the person that needs support.
Hence SC seemed the way to go, but then it was a bit too complicated for me to create.
Finally I found out about the -connect option of the winvnc.exe. It is very easy to set up.
1. I prepare my router to forward incoming requests on port 5500 to my machine in my LAN. (usually only required once)
2. I launch the UltraVNC listening viewer on my machine.
3. I ask the remote person to launch the UltraVNC server normally.
4. I inform the remote person about my IP-address.
5. Then the remote person must launch winvnc.exe -connect and in the dialog type my IP-address.
-> My screen shows the remote desktop.
If my IP address is constant the remote person can create a shortcut to launch winvnc.exe -connect ip-address.
The only thing slightly inconvenient is that the remote user must first launch the server winvnc.exe before winvnc.exe -connect will work. My wish is that in future calling winvnc.exe -connect also starts the server if not yet running.
Otherwise I would recommend this to everyone for whom the SC solution is a bit too complicated.
Cheers,
Joachim