Also if you are testing with the n900 on your local network via wifi then you will not need port forwarding for this just go direct to the IP address of the Windows machine.

Hint: not all routers allow you to connect from your local lan to the outside or internet IP address and then route back in via a port forward.

So you may need two RDP connections one for when you are on your lan and one when the n900 is connected directly to the internet.

rgds