if you can ping the linux box from the windows boxes, but you cannot telnet to it, then your linux box isnt renning telnet server. or your telnet client isnt working (or misconfigured), or your not on a LAN (maybe a router is filtering your telnet sessions or whatever).
<< what shoud i add/set to let other nodes of the network to "see" the linux box? >>
do you mean microsoft network neighborhood? cause linux (unless u configure samba) does not share files the way windows does, and you wont see it on the "network".
your linux box is gonna be there, but when you think of networking youre thinking of file sharing. and linux can do this great, you just need to use FTP or configure samba.