Prefetch files optimize application loading and booting up in Windows XP. They are a set of temporary files that help in loading Windows and other installed programs faster, and in a better way. Whenever you open a program, prefetch files save the information required for the program to load. The files help in loading the same program faster, when they are opened again. This is because the computer does not have to refer to the original source files, all over again.
How Prefetching Works
These files are the intermediate sources that provide instant information to the computer, helping it load various software on your computer, in a faster and quicker manner. They monitor the files and applications that you use over time.
The Windows XP Cache Manager monitors the data that is moving between the disk and RAM, as well as RAM and virtual memory, to help the prefetch operation improve its performance. The maps are then saved to files with '.pf' extensions, in a folder usually located at C:\Windows\Prefetch (if C is the drive label holding your system files).
So whenever an application is loaded, the Cache Manager will first check the Windows\Prefetch folder and find the corresponding map. When it finds one, it will directly access the directory and files in the map. The Memory Manager will be alerted and will be asked to use the information in the file to load data. This helps the applications and programs to respond faster and quicker.
Do these Files Need to be Deleted?
There is usually no need to delete these files, as they do not slow down your computer. However, they do use up memory, and therefore may be selectively cleaned, if need be. They help Windows in optimizing search operation during launch time. These are files that are rarely used. They are referred by the Cache Manager, only when a particular application is launched. And in any case, the folder only stores information about the last 128 programs, that have been recently accessed.