Pre-fetching (the reading of system boot files into a cache for faster loading) is a commonly overlooked component that can have a significant impact on system boot time.To see which files are gathered using each setting, clear the prefetch cache located at C:\Windows\Prefetch and then enable one of the settings listed in this hack.
Clear the cache and repeat for each setting. Set the Registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\ Memory Management\PrefetchParameters\EnablePrefetcher to 0 to disable prefetching, 1 to prefetch application launch files, 2 to prefetch boot files, or 3 to prefetch as many files as possible.
"Windows XP Tips: Alter Prefetch Parameters"
Reference : techpraveen.com