If you want a GUI which is closer to windows or OSX stick with KDE or Gnome (my preference) - if you want something a bit more streamlined then Fluxbox is groovy - my housemate's a bit of a whizz (been using Linux for years) and he uses fluxbox - it loads incredibly quickly and uses very few resources, which is a bonus on that older machine. 's not quite as user friendly for someone who's not used to using Linux, but then I suppose it forces you to get used to it
