It is a little late to answer your question, but it might be helpful for other people looking for answers to it.
I found that you can access X applications from a remote computer using SSH. This is probably a good and secure alternative to using VNC + VPN.
To access KDE from Windows, you need to install an X server in the Windows machine, and use the forwarding feature of SSH. I posted specific instructions in my blog at http://udogspot.blogspot.com/2009/02...m-windows.html
and I use PuTTY and Xming as the key tools to gain remote access to KDE.
An unfortunate disadvantage of this method is that it consumes a lot of bandwidth because the image quality is virtually perfect. It also consumes a lot of computer resources (in the Linux portion) because SSH needs to encrypt and decrypt information, which is pretty demanding.
Hope this was helpful