XP vs SERVER 2003 vs VISTA on INTERNET CONNECTION SHARING??? Which one is better than other both?

That really depends on what all you want the network to do. If you want to establish a domain with a static file sever then it is best to stay with a stable server platform like Server 2003. For home networking or connecting into a office network to use the resource XP pro and Vista seem to do equally well. (I would not suggest Vista if it is a main company resource, or if you are storing irreplacable information.) The only issue I have had with networking Vista to XP is that the log in commads are VERY restrictive. For example we use a no password computer as a print server / scanned document server at my office. Vista will not connect to it via a IP address string since it has no password, but you can still see it on the network map. As for the IPv6 address strings I have yet to test them since right now I am only useing Vista on one laptop, at least until I know it is stable enough to allow others to use. For basic internet connection sharing....in a home settig I stay with XP (Home or Pro) or Vista a server OS would be a little overkill.