The behavior of the Prefetcher is controlled with this DWORD registry key:
The Task Scheduler notifies when a process has started, causing the prefectcher to start monitoring the first 10 secs of the process start, and then saves the recorded disk activity caused by the process in a *.pf file in the Prefetch-directory:
[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Control \Session Manager\ Memory Management \PrefetchParameters]
EnablePrefetcher = 3 (Disabled = 0, Application = 1, BootUp = 2, Application AND BootUp = 3)
Note Windows Home and Professional edition will by default enable the prefetcher for both Application and BootUp. Windows Server edition will by default only enable the prefetcher to optimize bootup.
Note if using other values like 5 or 6 then it will either disable the prefetcher or only activate one of the prefetching types.
Note the Prefetcher is a service that runs in background and monitors disc and memory usage, and this monitoring requires CPU and RAM. If having less than 800 Mhz CPU and 512 MByte RAM, then one should consider only to enable the BootUp prefetcher.
More Info MS KB Q307498
The Prefetch-directory also contains a file Layout.ini, which is generated from the saved scenarios. The Layout.ini is used when doing a full defragmentation where frequently used files are aligned for faster loading. The Layout.ini is by default generated automatically, but one can also force the generation with command (Will run for 1-10 min):
C:\WinNT\Prefetch or C:\Windows\Prefetch
Note if deleting the contents of the prefetch directory, then it will loose all history of how to optimize the launch of application and will ruin the concept the prefetcher.
Note it can be a good idea to clear the prefetch directory when having applied a service pack for Windows or other applications, so the optimizer will quickly adapt to the updated files. Also if using AntiVira software, then this directory should be excluded to lower disc activity.
Note one can do a quick/partial defrag according to the Layout.ini, and only optimize the boot- and application- files for faster startup using Defrag.exe:
Note the generation of the Layout.ini and the partial defragmentation (dfrgntfs.exe) is automatically started when the computer is idle (or within every 3rd day). One can configure this automatic defragmentation of the computer with these registry keys:
defrag c: -b
More Info MS WHDC - Benchmarking on Windows XP
[HKEY_LOCAL_MACHINE \SOFTWARE \Microsoft \Windows \CurrentVersion \OptimalLayout]
EnableAutoLayout = 0 (Optimize Programs=1, Disabled = 0, Default = 1)
[HKEY_LOCAL_MACHINE \SOFTWARE \Microsoft \Dfrg \BootOptimizeFunction]
Enable = "Y" (Optimize Booting="Y", Disabled = "N", Default = "Y")
Note other processes also starts when the computer is registered as idle, so if having problems using the computer after it has been idle, then it is most likely caused by the Indexing Service.
More Info MS KB Q313300
More Info MS WHDC - Kernel Enhancements for Windows XP
More Info MS MSDN - Windows XP Kernel Improvements
Updated: 31 July 2010