We suggest you using port-forwarding. When a computer on the internet sends data to the external ip address of the router, the router needs to know what to do with the data. Port Forwarding simply tells the router which computer on the local area network to send the data to. When you have port forwarding rules set up, your router takes the data off of the external ip address:port number and sends that data to an internal ip address:port number. Port Forwarding rules are created per port. So a rule set up for port 53 will only work for port 53.
More information on port-forwarding you can find here: http://www.portforward.com/help/portforwarding.htm
Please, visit this page, find you router model and follow the onpage instructions:
1) that PC with Radmin server has an access to Radmin activation server PC
2) that you've entered correctly your license key and address/port of you activation server to .msi if you are unsure please create a tech support ticket and attach a screenshot of these pages in .msi
I suppose you can connect in command line mode and start any application which reverts PC from full-screen DOS mode to a normal one. It greatly depends on your DOS application, but even starting video could help.