Kvpnc, vpn and vnc connections?

I’m having difficulty in connecting to a windows network domain from Opensuse 11 - I am trying to establish a vpn using Kvpnc and then use realvnc to connect control a pc on the remote windows network. I can successfully do this using windows (establishing a vpn and then starting RealVNC viewer) but am having no success at all in Linux. Can anyone point me in the direction of where I can find the correct settings for these connections (do I have to use a PPTP connection for a Windows network?) and also settings and services required in the Firewall? I suspect I don’t have the correct settings.
Any help much appreciated.

First things first, can you connect to the VPN concentrator in Linux? If so, can you ping the host you’re trying to connect to?

What VNC server are they using on the Windows box?