Who needs Windows Vista? According to Yahoo news, Windows Service Pack 3 will offer substantial performance gains:
Running an Office productivity test suite on a preview version of Service Pack 3 for Windows XP, Devil Mountain discovered a 10 percent performance boost over the current version of Windows XP, the company reported on its blog. So Vista's biggest competition isn't Apple or Novell or Red Hat; it's Microsoft itself, it's XP.
=> Read more: Windows XP Speed Boost Coming with SP3