Windows PreFetch - Comments Page 1

I would like to thank you for publishing your hints and fixes. I have spent the better of two days trying to increase the speed of my grandaughters computer. I took most of the information provided by you in, "Make windows XP run faster". After applying the suggestions and adding an X-ray program you suggested, her old machine is working much better and the speed has increased. She is happy with it now and that is the main thing. She also thinks I am a genius. I don't think I am going to tell her that the real genius is you. Thanks again.

Related to this is perhaps another Myth: There exists software which enables the operating system to be tailored only for the application being used. Consequently this pairs down all the unnecessary processes and calls. Apparently it is able to search for all the drivers used by an application and match them with windows,and shuts down everything that is not vital to the application being used. This way all the memory and cpu power is devoted only to the desired application. Is there such a thing? I have not seen it anywhere. And if not what is the next best thing to optimize PC performance and speed with respect to Windows?

EDITOR'S NOTE: That's the job of the operating system to allocate resources to the task at hand, manage the cache, etc., to optimize performance. I wouldn't use such a tool, because it might end up fighting with the OS.

Is X-Ray capable of speeding up My PC significantly?

EDITOR'S NOTE: It depends what you do with it. X-RayPC shows you everything that's running, and gives you the option to kill running tasks, and optionally remove them from the Startup list. Use with caution, it's a power tool.

So why not tell those of us who may have disabled prefetch how to restore it?

EDITOR'S NOTE: To re-enable prefetch, run REGEDIT. Locate HKEY_LOCAL_MACHINE -> SYSTEM -> CurrentControlSet -> Control -> Session Manager -> Memory management -> PrefetchParameters. Set the value of EnablePrefetcher back to the default value of 3.

Then whats the difference between X-rayPC and MSConfig? You can stop programs from startup as well. IF it goes further than task manager and config are you implying ways to suspend unnecessary Windows programs ? Where can I get X-ray?

EDITOR'S NOTE: X-RAYPC shows all running tasks, and every program that runs automatically at startup, all on one screen. Think of it as MSCONFIG + Task Manager, on steroids. I do not recommend it for novice users, because you can do damage to your system if not very careful.

See http://www.x-raypc.com

Just for grins, I had to try it, and see. I deleted the contents of \Windows\Prefetch (all 322 entries), and... bang! My "boot" time decreased by 22 seconds. That's empirical observation. What can I say, except... "Your mileage may vary".

EDITOR'S NOTE: Okay, but I imagine your frequently used programs loaded a bit slower the first time you opened them. I checked my prefetch folder and found only about 20 entries, none of which were more than a week old.

I deleted windows prefetch accidentally, what should i do?

EDITOR'S NOTE: Don't do anything... Windows will rebuild it for you.

If you have over 128 prefetch files that means you system has either not been rebooted in some time, not allowed to go idle or the prefetcher is broken in some way. On a properly working system the folder is self cleaning at 128 entries. Regardless extra files do nothing but take up disk space. To learn more about these Myths read: http://mywebpages.comcast.net/SupportCD/XPMyths.html

CCleaner can get rid of OLD prefetch data. I'm assuming that is just prefetch data that hasn't been used in a while. I know Windows is supposed to do that automatically, but it isn't perfect and a third party program can clean up behind the Windows automatic process. Just a little more info. It was a good a read and well written.

This is one of the best forums. I use CCleaner weekly. My Prefecth has only 39 entires. Noticed that all of them are programs I use daily and only one entry is 2/12/07. Bob, you are right. XRay is on steroids. Showed me things I hadn't seen with other programs.

Windows XP AUTOMATICALLY cleans the folder on que when the 128 limit is reached (not before) and leaves the most used 32 prefetch apps. You should NEVER delete a prefetch file for an installed application. CCleaner irresponsibly uses the NTFS last access date stamp to delete prefetch files. Do NOT use the CCleaner option to clean "old prefetch data", if you have the NTFS last access date stamp off CCleaner will delete the entire folder!

There's a flaw in the logic behind the windows prefetch.

It doesn't reduce load time, it just shifts the load time to an earlier stage (aka boot time, when you're most likely AFK getting a cup of coffee).

If it could predict what program I am about to start then that would be good, but it can't and it doesn't. It just checks what software that is started and then keeps it in the prefetch until they time out. For it to actually work it would need to track each file over time and check how frequently I call for that file to judge if it should be preloaded.

On this 3 hour old install there's 58 files in prefetch, including system services that I've deactivated, several pieces of install software and even components that I've deinstalled. The fact that I use a program once, doesn't mean that I want it prefetched. XP tries to be smart and clean out old unused entries but it takes time.

Switching prefetch off and adding firefox to autostart has lowered my morning blood pressure a lot. But I agree that you shouldn't fiddle directly with the files. Just switch it off and let it settle.

So, after reading a LOT of articles on Prefetch I can only say one thing: YOU ARE BOTH WRONG! Prefetch does pre-map the memory for the processes, so deleting it won't bring much; but when it prefetches every application you run, it cost time to load that information and slows down the kernel A LOT.

Notice, if you choose "Boot-time only" option, Prefetch will only cache the drivers(!), and all that AV and system tray soft will stay slow. If you choose "Applications and boot-time"(default) it will POLUTE. As usual.

So, long talk, short meaning, as some say, here is the solution:

1. Clean the prefetch folder.

2. Reboot, open programs u usually open- do this 5 times. Now you have the IDEAL contents for your PC.

3. Copy Prefetch'ed contents to some directory, or 7z it...

4. Write a simple CMD script:

4.1.Clean Prefetch

4.2.Copy or extract IDEAL contents to the prefetch dir.

Execute this script on every reboot or so, and voila!

Happened to come across this odd behavior on my home system; had multiple wifi LAN cards, and seemed that one of them in particular was mis-behaving. Attempted to uninstall the driver for the misbehaving one, and this failed. Had to go to "Safe Mode" because I couldn't delete the directory that contained the program files (under "Program Files").

Rebooted. THERES A GHOST ON MY BOX ! It's still running ! How could this be ? Looks like there's still a copy in the prefetch. Will clear the prefetch and see if it's really gone now. Bottom line - looks like this great MS software loads images of files that aren't even on the disk anymore. It isn't even sitting in the Recycle bin; it's completely gone. Yet it's memory lives on in the prefetch. So I'll clean this crap up and see if things improve.

EDITOR'S NOTE: I'd be very surprised if the problem was Prefetch. My guess is that that failed uninstall has something to do with the driver still being loaded. Let us know!

How can you stop Prefetch causing IE8 to remember the old height of an image even when the actual image height has been altered? Even if an image is rotated through 90 degrees using Paint Shop Pro and re-saved, Prefetch seems to keep the old height for IE8 to use. I deleted wscntfy.exe...pf in Prefetch when the computer was not running Windows and sometimes it worked and allowed IE8 to see the correct height, but sometimes it did not. The only way I could get IE to see the new height was to rename the folder containing the image.

Finally, a website at the top of Google results that actually has the right freaking answer.

For those who are having issues OR want to test *properly*, do this *first*:

Start > Run... >

rundll32 advapi32,ProcessIdleTasks

(That last part is case sensitive.)

This will allow the prefetcher to clean itself out, optimize your MFT (to remove placebo speed boosts you mis-attributed to deleting prefetch entries), and anything else that has been waiting forever.

So: ProcessIdleTasks, reboot, reboot again and time this second reboot. Delete all your prefetch entries and then time it again.

I'd like to note, that all this applies to desktop computers. If a machine is primarily used to run an application server, just the process of monitoring used files and keeping the prefetch data could well be counter-productive. Still, this doesn't apply to the general home installation.

None of this "don't delete prefetch files" advice makes much sense. Common logic: prefetch files, when combined, take up megabytes of disc space that you most likely need to use. These "trace" files are only duplicated again and again - for instance, if you use your registry mechanic/cleaning program, a registry mechanic trace file shows up in prefetch - then use it again, and a minute later there's another. What's the point? Also there's mention of Windows automatically deleting unused files from prefetch after a while. This gives Windows too much credit. I noticed after a week that almost none of the files were being automatically edited, and I run a pretty smooth ship on my computer, so I could only blame Windows. All things considered, I'd say clean out prefetch as often as possible. Your computer can run fine without the files stored there "helping" it - and you're freeing up at least a few hundred kilobytes. Not much, but every little bit counts.

EDITOR'S NOTE: Dude, the 80's are gone. Hard drives are bigger, faster and cheaper. You can get a TERABYTE drive (1000 gigabytes) for $200 now. Don't sweat the kilobytes.

The author is correct, "cleaning" prefetch files will impair performance. However, many responders clearly do not understand how prefetch really works. Application prefetch files are used to optimize the loading of applications, not preload them. These files are referenced only after application launch has been initiated, not at boot time. A prefetch file will NEVER cause an application to load. Rarely used or unused prefetch entries will have virtually no impact on performance.

When an application loads, the system does not load all of it into memory immediately. It is loaded only as needed and then cached for later use. This system of loading isn't particularly efficient. The prefetch system keeps track of an application's initial requirements and saves an index in the associated prefetch file. On later program loads the system is able to "prefetch" this data into cache before it is actually required, thus improving performance. But note well, none of this takes place until application launch has been initiated. Deletion of prefetch files will deprive Windows of a valuable resource.

Microsoft's use of the term "prefetch" was unfortunate. While technically true, it has caused many to misinterpret it's meaning. As a result we have the widespread "clean the prefetch" myth.

Larry Miller

Microsoft MCSA

How is anything in prefetch loaded before the kernel? No way! PreFetch itself obviousely relies on it. Also, people here claim faster startup time by haveing the correct (word of emphasis) files in the PreFetchand and claim to have timed it so that it is an unmistakable fact. My point is certain files should be there; most shouldn't and there should be a fairly user-friendly way to achive this. Volvan was onto something.