Put the machine into the DMZ.
As that is easy to find out more about the DMZ on google, I'll stop here.
How can I set up the computer(win XP) and router in order to expose the computer to internet .
So, public can fto in and out to this computer .
The computer is connect to the router that use PPPOE to access internet .
The computer is connected the router by direct cable
The router is TP link TL-WR740N.