It sounds like you wish this to be a file server within the network. You could use windows file sharing, the nice drag and drop interface is pleasant enough, although it sometimes crashes computers, and makes them less stable overall, but, generally, it offers good speeds for file transfers. But, usually the best option is FTP. The protocol delivers very fast speeds, and there are many easy to use, easy on the resources, robust, and very configurable FTP servers out there. A quick search on download.com will yield many results.
I have heard the IPX is very fast, I have yet to confirm that, but, it's always an option, going to have to try it out on my network, when and if I do, I'll post whether or not it was fast.