The great thing about UltrVNC is that it lets me set up a d/l executable that is executed by the end user and therefore, bypasses any firewall port forwarding settings on the client end. THe server end needs PORT 5900 forwarded to the machine running “Ultra VNC Viewer (Listen Mode)”.
The full Download for UVNC is here: http://www.uvnc.com/download/index.html
And the app that makes all of my remote support magic happen is Ultra VNC Single Click: http://www.uvnc.com/addons/singleclick.html