S: Virtual shared LAN folder

Hoi,
I am looking for a software fits these needs:
Multiple PCs are connected via LAN (Windows, TCP/IP).
The software create a virtual directory in which all public files are listed.
If i want to have such a file the client fetches the file from the source and
all other computers in the lan which have the file or parts of it.
It's important that the software is easy to use, explorer style.
I want to achieve the fast distribution of files across all connected PCs on the LAN.

Any idea?
Thanks