Prefetch files are the files that slow down Windows boot up. That is, these files cause windows to start up slower than the usual.
How do these prefetch files slow down the PC?
When you turn on your PC, you see windowsXP logo with a progress bar at the bottom. When this screen appears windows scans the prefetch folder. That is, if there are many files inside the prefetxh folder, then it will take considerably long for windows to start up. In other words, prefetch files are scanned at the startup of windows and windows load only after scanning these files inside the prefetch folder.
You can delete prefetch files from your computer to speed up startup of windows and hence speed up your computer.
How to do it
1. Navigate to C:\windows
2. Now find the folder prefetch
3. Now you are at adress- C:\windows\Prefetch
4. Now delete all the files you see in the folder. Don't panic, it wont affect the working of your windows.
Here is a screenshot of my prefetch folder:
Your prefetch folder is empty and now the boot time of your computer is faster than it was before.