Halo 2 Vista & XP Problem

[UnReaL596]

Ok so i have Halo 2 on XP & vista, And i have a problem for each one, On XP i can log into live but when i try to join a game i always get (Unable To Join This Party) On Vista i can't click on Network or Live its all Grey colored meaning not clickable, I have a sliver account but i should be able to play online right? they have sliver & gold servers.... meaning i can join the sliver ones? So i really don't get this at all, Any help?

[Ifafudafi]

XP is not supported by H2V, as detailed in http://www.h2vista.net/forums/announcement.php?f=28, and therefore will cause problems; most notably the inability to play online. As for the Vista issue, make sure your account is not offline-only by checking that it has "Games for Windows LIVE" below the Gamertag name, and that a button saying "Join LIVE" doesn't pop up when accessing the dashboard.

If you haven't updated your copy of H2V or GFW:L Redistributable, you should do that too.