Make sure both host and client machines are functioning on the same network (try pinging the host from the client) ans make sure the share privledges are such so as to allow people to access it. You should be prompted for a password to connect I believe, and that should be either a net admin cred, or admin on the host at least.
Also, is it an actual domain (with a properly config'd DC)? Or is it a workgroup? Quite different... if its a domain, you may have incorrect config with your dc....