What is the purpose of the Prefetch folder?

[awonson]

I would like to know what the purpose is of the Prefetch folder in the Windows folder in XP Pro. Is it some sort of cache? And can I delete the files in it?
Thanks, Andrew.

[M@CHINEHE@D]

The Prefetch folder in your Windows directory is used to store information on the applications that you always open, this will speed up the loading time the next time you open it again. It is not advisable to delete it frequently as it will need time to collect the information again. Deleting the contents in the Prefetch folder about once a month should be alright, that's what I do depending on how many different applications I open during those period. Once fresh it will normally take 3 boot ups before Windows collect enough information for the applications that you run.

If you find that your Prefect folder is always empty after boot up it could be that your Task Schedular is disabled.

Type "services.msc" without the double quote in Run and look for Task Schedular. The Status should be "Started" and Startup Type should be "Automatic". If it's not automatic then set it to automatic and reboot. This should solve your problem. If I'm not mistaken, the registry setting for you prefetch is by default at 3.

Hope this helps.

[jenae]

Hi this is an attempt to speed things up , and as a first effort it works quite well, however there are possible problems, this subject has not been discussed as much as it might. In future OS this will be one of the key features(according to MS) So for those interested this from Kelly's XP:-
Prefetch is a new and very useful technique in Windows XP. However, after using XP some time, the Prefetch directory can get full and have obsolete links in the Prefetch catalog, which can slow down your computer significantly.

The Prefetcher component in Windows XP is part of the Memory Manager, and helps to shorten the amount of time it takes to start Windows and programs.

Windows XP "monitors" itself and notices which applications are launched frequently. It gathers information about these applications and what they access with the launch and stores this information in the prefetch folder. It then uses this information to "optimize" access to these files so that they launch faster.

Once every three days, by default, Windows XP will perform a partial defragmentation and adjust the layout of the disk based upon current use. The files to be moved are written in the file Layout.ini (found in the Prefetch directory under the System Root directory).

Suggestion: Open C:\Windows\Prefetch and delete the obsolete files, reboot. However, if you don't have a real good
reason to delete these files, just leave them be. Let the system handle this folder.

If system performance is an issue:

XP automatically optimizes itself every three days, bootvis forces the optimization to happen now rather than having to wait three days. Fast Boot /Fast Resume Design: A performance trace visualization tool for use with Windows XP systems.

Bootvis can be downloaded here. For more information click here.

Manage the Windows Prefetcher Service: Go to Start/Run/Regedit and navigate to this key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters

Create a new DWORD value, or modify the existing value, called "EnablePrefetcher" and set it according to
(0 = disabled, 1 = Application launch prefetching, 2 = Boot prefetching, 3 = Both prefetching). To clear the Prefetcher cache, delete all the files in the Prefetch sub-directory (e.g. "C:\Windows\Prefetch").

Prefetch Defined: This directory is used by the defrag utility to help organize the files on your PC for more efficient
loading.

"I/O performance is strongly influenced by the layout of files on disk. Files and directories that are heavily fragmented or dispersed across the disk will hurt performance. While Windows XP will automatically reposition some files to improve performance, this will generally be done infrequently and will usually include only a small fraction of the files on the disk.
Therefore, it is a good idea to defragment the disk following an installation.

Once every three days, by default, Windows XP will perform a partial defragmentation and adjust the layout of the disk based upon current use. The files to be moved are written in the file Layout.ini (found in the Prefetch directory under the System Root directory)." Windows XP Performance

Boot Prefetching
Windows XP speeds up system boot by observing the code and data needed each time the system is booted and prefetching the necessary file contents early in the boot process. This prefetching is not done until the third boot of the system, when sufficient information is available to make the prefetching most effective. The files observed during system boot will be used in the disk layout process mentioned above. Additional information on the prefetcher and the Windows XP boot process can be found at Fast Boot/Fast Resume for the Windows Platform.

Application-Launch Prefetching
Windows XP also uses prefetching when launching applications. The files and the contents of the files accessed by each new process are observed and recorded. No prefetching can be done for the first launch of an application, so first launches are often considerably slower than subsequent launches. About 85% to 90% of the improvement is realized after just one launch of an application, with the remaining speed improvement coming after the system has had an opportunity to adjust the disk layout with information specific to this application. Benchmarking on Windows XP.

[DuaneB]

Apparantly, XP is taking care of my Prefetch folder automatically. It never fills to a point that I feel it needs emptying. I just checked it and I have 123 files with the oldest being from July 9th.