What can I do to make sure that the prefetch feature is active in my Windows Vista ?
In the search box on the start menu type
If you need to enable it, you can double click on the service and set Startup Type to automatic and reboot.
The registry key
To change the value, double-click it. You'll then see the Edit DWORD Value screen. Enter the value representing the level of prefetching you want in the Value Data field.
Verify that it is set it to 3.