GTK are for Gnome envireoments, this are not available for windows os. You cant. If you want to use some gaia things for windows check out at gaia10.us there is a windows blinds skin but nothing specialy made for XP just for windows 7.
tocayo, eso es una lastima... no solo el volver a Empathy sino el usar facebook en pidgin ... facebook daña todo porque es la plaga mas grande del siglo XXI no puedo (ni quiero) ayudarte con ese issue xD so... sorry
That line looks like that just because I was using Gaia 10 GTK and Emerald. If you see the other link I put on the comments to see it in action with an screenshot of mine, I was using gaia sprout gtk and emerald another theme and there is no brown line, remember that pidgin uses the interface of your current Gtk. Thanks for install