Boosting Vista Startup Performance
A quick way to boost the startup performance of a computer running Vista is to disable the SuperFetch features.
To disable the SuperFetch service, use the Services console from Administrative tools to stop the service and then set the startup value of the service to Disabled.
Once you do this you should be able to boot your computer, log on to Vista, and start working immediately instead of having to wait several minutes (or longer) for your system to become responsive. If you don't disable SuperFetch, chances are your disk will thrash and CPU usage hit the roof for several minutes after rebooting and logging on.
Disabling SuperFetch will also enable Vista to go into sleep mode more quickly and to resume from sleep faster as well.