"David Short, an IBM consultant who works in the Global Services Division and has been beta testing Vista for two years, says users should consider 4GB of RAM if they really want optimum Vista performance. With Vista's minimum requirement of 512MB of RAM, Vista will deliver performance that's 'sub-XP,' he says. (Dell and others recommend 2GB.) One reason: SuperFetch, which fetches applications and data, and feeds them into RAM to make them accessible more quickly. More RAM means more caching."