[swerdna]

RDP usually uses one channel; viz port 3389. So you can forward the port through the modem to the mandrake 6 machine. You can forward it on from there to the router and then to a windows machine. NB I think this can be forwarded to only one machine. So if you wanted to interact with all windows machines it could perhaps be like this:

You could RDP connect to the Mandrake machine and then from an active desktop on the Mandrake machine you could choose at will connect further using port forwarding across the router to a machine of your choice, once you had the mandrake desktop open.

OR

You could rdp connect to alwaysthe same computer on the LAN of windows xp computers and from there you could activate a VNC or an RDP connection to any other computer on the LAN.

I think the latter method deserves the priority investigation because it might be best just to port forward through the Mandriva machine and router to a modern operating system windows xp. Mandrake is very old -- outdated technology -- I'm thinking you should skip through it.

Here's the showstopper question: can Mandriva 6 handle rdp protocol and port forwarding at all? maybe not because RDP was invented after Mandrake 6, perhaps?

I would think about updating the O/S on the front machine, but then there's this question: can the front machine handle a modern O/S?

So in the end I personally would throw out the front machine and connect the modem to the router direct. Modern O/Ses have pretty strong firewalls and the firewall in the router adds to that.

And I would probably look at VNC because the remote client can target any computer on the LAN whereas RDP can (I think) only target one.