web server != file server
how about setting up a network share, vpn, p2p, or good ol' ftp?
iis is already on windows and it's free. just activate it and enable directory browsing.
is there some specific reason you need to enable it on :80?
Personally if the need arises I just enable the HTTP server on my Everything search: http://voidtools.com/ (334KB download) - usually because I have no idea where any of the files I am looking for are anyway, having a search built into the HTTP server is a big help