What is a prefetch file ?
A Prefetch file is one which contains information about the files loaded by the application is created by Windows operating system. The information in the -Prefetch file is used for optimizing the loading time of the application in the next time that you run it.
WinPrefetchView is a free to use utility which allows you read and see the content of .pf [ prefetch ] files. By looking in these files, you can learn which files every application is using, and which files are loaded on Windows boot when you start your computer. Removing the unnecessary prefetch files can boost the speed of your computer.
Cleaning the prefetch folder [ C:\Windows\Prefetch ] and removing the unused and unnecessary prefetch files can boots up the speed on your PC, here is another free program which allows you to clean up the unused prefect files from the windows prefetch folder.
Here is the screenshot of this program – Windows XP Prefetch Clean and Control – which deletes the prefect files from your computer in a safer way.
However this program was released for windows xp, but it may work for vista and Windows 7 too, you can try at your end.