There’s no hard evidence that enabling or disabling this service will increase performance in general, but if you open and close applications often you should definitely leave it alone. You will have to test your configuration to know for sure.
Note that I don’t recommend disabling this service, but we try to cover how to do everything on Vista.
Open up Services in Control Panel or by typing services.msc into the Start menu search or run boxes.
Double-click on Superfetch in the list to open up the properties, and then change the drop-down to “Disabled”. You can also click Stop to immediately turn it off.
I don’t recommend this tweak for regular users, but somebody might find it useful.
