I never liked those home-hacked things, preferring to know exactly what alterations I've made myself.
You can do that sort of thing on any xp, though. Lookie here: http://kadaitcha.cx/performance.html (scroll down a bit).
Found a few sites for tweaking Vista as well. Here's one: http://www.tweakvista.com/VistaPerformanceTweaks.aspx (not seen any reviews of it, and can't be arsed going through everything, so use at your own peril). And don't bother with the utility on there, just those articles.
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