Information about your most frequently used programs is saved by Windows 8 and 8.1 as prefetch files in the Prefetch folder. By using these prefetch files, Windows can speed up the loading of your applications considerably -- but because the Prefetch folder can store up to 1024 files, it can increase in size over time. To free up some disk space on the system drive, delete the prefetch files during periodic maintenance.
Erase the Prefetch Files
Press "Windows-X" to display the Power User menu and click "File Explorer" to launch the utility.
Select the system drive. The system drive is the drive where Microsoft Windows is installed -- usually C:. Double-click the "Windows" folder to open it. If one of the administrators has hidden the folder, click the "View" tab in File Explorer and then check the "Hidden items" box in the Show/Hide group.
Open the "Prefetch" folder. All prefetch files created by Windows are stored here. These are binary files, so you can't open them in a text editor; the files are not designed to be read by humans.
Select the prefetch files you want to delete, press "Delete" and click "Yes" to confirm your action and delete the files. To select everything in the folder, press "Ctrl-A." To select several files, hold "Ctrl" and click each file.
A prefetch file contains the name of the program and its location on the hard drive, information about the files loaded by the application when you launch it, and information about the number of times the program was launched and when it was launched. Furthermore, the file contains the version of your Windows operating system.
These binary files, although not designed to be read by humans, are used during digital forensics investigations by investigators. In fact, prefetch files are often a great source of evidence in criminal cases.
Every time you launch a program on your Windows computer, a prefetch file is created. If there are already 1024 files in the Prefetch folder, Windows automatically deletes the oldest one.
The Prefetch folder contains prefetch files for programs that have been uninstalled. In some cases, a large Prefetch folder causes a slow boot-up.
You can disable the prefetch service or force it to only cache boot system files to avoid slowing down the boot-up process. Type "regedit" on the Start screen and click "regedit" in the list of results to open the Registry Editor. Open the "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters" key and double-click the "EnablePrefetcher" value. Change the "Value data" field to "0" to disable the prefetch system or to "2" to cache only boot files. If you change it to "1," only programs are cached. If you set it to "3," both programs and boot files are cached.
You programs may open slower than usual after you delete the prefetch files.
Do not delete the "Prefetch" folder itself. Windows needs it to create new prefetch files and may not be able to recreate it automatically.