There're two ways to do what you want, and they aren't old stuff ;)
Do it in the server side:
http://realvnc.com/products/free/4.1/winvnc.html#Sharing
Check the "Always treat new connections as shared"
As a side note, if you need to occasionally share connection,
open VNC viewer's
I want to connect multiple clients to 1 server. Whenever I connect a 2nd
client the first is forced off. I searched the forum and found some old
stuff about changing a registry setting but that apparently does not apply
to version 4.1.2 (on Windows 2000). I cannot see any configuration options
