horseman had a good idea about norton commander but it won't work via dosbox. and i'm not sure if there was tcp/ip protocol in dos at all. you will need to instal IPX protocol on your xp machine (which is quite easy in control panel-> network managment) and then get some dos lan client and somehow configure the lan in dos=S but i don't know how
random google search gave me this result
http://www.computing.net/dos/wwwboard/forum/14970.html