This feature was suppose to be Longhorn exclusive and it makes the OS load the applications 15% faster, boot 50% faster and install patches with 50% less reboots than it used to.
The only reason why its faster is they added a SuperFetch feature to the Prefetcher. If you look at the key in RegEdit:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SessionManager\Memory Management\PrefetcherIn Windows XP you will notice:
EnablePrefetcher = 3and in Windows Longhorn you will notice:
EnableSuperfetch = 1
You can put the "Enable Superfetch = 1" in Windows XP and get the same speed as Longhorn!
Requires Windows XP SP2 and above.