Equally uncertain from testing so far is whether there's any perceptible performance gain from two application-load hastening techniques, . SuperFetch is an upgrade to the pre-fetch capabilities of earlier versions of Windows. It keeps close tabs on the applications you use most frequently, and preloads them into memory. SuperFetch is date-aware, and is even able to differentiate between programs launched on weekdays or weekends. The goal is to speed up the start-up times for the applications you use most. ReadyBoost adds a memory store for SuperFetch by harnessing user-supplied USB 2.0 keys or other flash-based memory, such as CF or SD cards.

This pair of features may sound more cool than they are. To date, we've seen little noticeable difference through the use of these tools. But if you frequently launch AutoCAD or Photoshop, it might be a lot more noticeable.

We'll have to wait and see what's real and what's marketing, but there's at least a good chance that Microsoft will make good on some aspects of its performance and reliability claims for Vista. One of the bog-down points for performance is the Windows System Registry, which among other things, is edited by every application you install, making it susceptible to bloat and corruption.

Largely for security and application-compatibility reasons, Microsoft is introducing a Registry-virtualization technique that limits installing applications' access to the Registry but fools them into thinking they have in fact edited the Registry. This feature was needed to support Vista's new, better protected namespace (that is, the locations of systems and applications files and special folders). But this Registry-virtualization trick may also keep the Registry healthier over time.

Under the hood