I read this on a site:
Myth - "Deleting the contents of the Prefetch folder improves performance"
Reality - "Every time you delete an application's Prefetch (.PF) file you will cripple that application's load time the next time you go to launch it. This can temporarily increase load times by as much as 100%. For one thing, XP will just re-create the Prefetch (.PF) trace files anyway; secondly, it trims the files if there's ever more than 128 of them so that it doesn't needlessly consume space. However you do not regain optimal application load times back until after the second time you launch the same application due to the Prefetch (.PF) trace file being re-created. Prefetch (.PF) trace files are not a cache and are not preloaded into memory upon windows startup. They are never even accessed until you launch an application. Only one Prefetch (.PF) trace file per application is created. There is never ANY reason to delete these files. Cleaning the Prefetch folder is actually a temporary self-inflicted unoptimization. Why you would want to deliberately hurt your PC's performance I have no idea."
Prefetch on my PC only equals to 5.88MB...
TURNING IT ON:
As with most Windows XP-related things, you can change the way that Prefetch behaves by making a change in the registry. For low-memory systems, you can even completely disable the feature, which ensures that every last byte of RAM goes toward running current programs, not the ones XP guesses you'll need next.
To change the registry settings for prefetching, start the Registry Editor by selecting Run from the Start menu, typing regedit in the Open text box, and clicking OK. When the Registry Editor window opens, navigate through the left pane until you get to this hive:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager\Memory Management\PrefetchParameters
In the right pane, look for the key named EnablePrefetcher. The value of this key represents how prefetch works on your system. Values you can choose from include:
* 1—Application Launch Prefetch
* 2—Boot Prefetch
* 3—Prefetch everything
To change the value, double-click it. You'll then see the Edit DWORD Value screen. Enter the value representing the level of prefetching you want in the Value Data field.
As a general rule, if you're on a low-memory workstation, 128 MB or so, set the value to 0. If your workstation has 512 MB of RAM or more, set it to 3. Otherwise, you can choose the value as best suits your needs and observations.
This also seems good advice:
As you can see, just like the TEMP directory on your system, the Prefetch folder can fill up with lots of unused entries. You can improve system performance by deleting files from this folder.
In doing so, you have two choices: You can selectively delete very old files and files for programs you rarely use, or you can batch-delete all of the entries in the folder. Of the two methods, the mass deletion is probably the most efficient. Windows XP will automatically reprefetch programs when your workstation restarts anyway, so the most frequently used programs will reappear automatically.
To delete all the files, simply select them all in Explorer and press [Delete]. You can also create a batch file that you can run periodically to do the job for you. Just open a command prompt, type copy con killpref.bat, and press [Enter]. Next, type the following commands:
del c:\windows\prefetch\*.* /q
Finish by pressing [F6] and then [Enter]. You can then run the killpref.bat file from the command line or Explorer window, or run it as a scheduled task. It will automatically empty your Prefetch folder. When you restart your workstation, it may initially boot a little slower and load programs slowly, but as the prefetching kicks in again, frequently used programs will start quickly again."
i hope this helps