Hi all,
I have really a newb question. I was wondering if by installing a p2p client on a Linux machine (e.g. bittorrent, emule, limewire) it was possible to exchange file with users having a Windows machine.
Thx

I guess you COULD do it that way, but why? SAMBA would be better suited for that, even ftp would be a better way to do that. I would suggest having a look at setting up Samba though

The EASIEST way to share files is to install the openssh server (which includes sftp, for transferring files) on the Linux machine, and install WinSCP on the Windows machines. Then, use WinSCP to connect to the Linux machine (you will need to know its ip address; type ifconfig at the command line on the server), and you can copy files easily.

This solution is one way though - it doesn't help you access files on the windows machine from the Linux machine. Though you can use the same basic idea, if you obtain an ssh and sftp server for Windows.

samba is a good way to get files back and forth because it is alrdy built into windows and simple to configure in linux. You could also go the ftp route. The drawbacks to those are that they are incredibly slower in comparison to the SFTP (ssh) route that cantab just mentioned. SSH is also extremely simple to configure, but i would recommend looking into RSA encryption if you plan on doing that, or make a different user account on the server with strict permissions. Another route, which seems to be a tad faster than SSH is NFS. Setup on that is not as easy, but it's a lot safer from a security standpoint, and way more streamlined once its up and running (install windows client and its built into windows explorer, just mount as network drive).

This is absolutely possible and in fact there is no problem at all. The client will only give you the means to access and participate in a given peer to peer network, e.g. bittorrent, edonkey, kademlia, etc. The operating system is outside that domain. Protocols, well defined & standard protocol are the same, independent of the OS.

You might be missing one thing.
The majority of windows programs will not run on linux and visa versa.

Some windows programs will run on linux using a 32 bit windows emulator (WINE). It takes some messing around to get them to work.