sshreach.me can be used to access either Windows or Mac machines using VNC. To create sshreach.me client for VNC, you need to forward port 5900 (unless you have changed your VNC server's listening port).
Once your client is created, just download and activate it (for instructions on how to activate client script under Windows, read here). After you've opened a tunnel through our web interface, you just need to point your VNC client to the provided tunnel endpoint. And since your connection will be made through our forwarding server, it means that your VNC connection will automatically be encrypted through ssh.