Thanks a lot Spike for your kind and quick reply!
regarding manifests: ok
regarding compiling: ok -I'm installing cygwin, let's see. I'm always thinking that a working Visual Studio 2012/2013 and CodeBlocks installation could be a lot better for Windows devs
regarding dedicated argument: ok, so.. no arguments! The wierd thing is that I changed sv_playerslots "4" in C:\Users\myuser\Documents\My Games\FTE QuakeWorld\fte\ftesrv.cfg but server keeps disconnect fisrt player when second player (second istance of fteglqw.exe ON THE SAME computer) connects. Could it be a network problem? Or there is a .cfgs hierarchy? Couldn't it be possible to use just one cfg? There are too many and I couldn't find a good guide about Quake cfgs (fte has even its own one!)
regarding sprites: ok, just curiosity
regarding firewall: this one is tricky. I tried even to shut down Windows Firewall, but sometimes server hangs up(I can't type input anymore in the server console when it happens), no matter if the firewall is on or off. In this cases, client (obviously) waits forever a connection. This freaks me a little out, because the availability of connection seems (I could have done lots of errors so I'm not 100% sure) a little unpredictable. And, for a commercial game, this is not an option.
regarding huge datagram: that was my fault. I used a quake id1 folder mixed with dp and fte stuff. One of them was the great "Quake Small Mod Compilation" by Seven. Maybe that was too big, I don't know. Again, that's not good too. For a commercial game I'd like to pump up graphics to make it look better but if network (even locally!) can't handle it.. I'm stuck! As I stated before, that could be a mess made by myself, so, for now, let's just forget what I said!

I'm stuck anyway with making (just for start) a simple test connection with 2 or more players with FTE and normal Quake. Where I'm wrong? Why server always kicks last player when another client approaches?
Thanks again Spike for your help