have you considered Tversity?
it works fairly well.
personally, if you are considering streaming video, i'd recommend
connecting to the "server" pc by ethernet. streaming wirelessly
is very hit and miss using 802.11g (54Mbps).
it's a pity that the Wii doesn't support 802.11a (54Mbps / 5Ghz)
as per the xbox 360.....that protocol is excellent for video