Will Tweaking Windows’ Prefetch Folder Allow for a Faster Startup?

Myths about optimizing Windows have been floating around forever. Unfortunately, a couple of technical Windows books, magazines, and Web sites have picked up on them by accident as well. In some cases, these rumors are pretty harmless. For instance, someone at a technical forum started the rumor that SuperFetch, a Vista feature that enables programs and files to load faster, is also available for Windows XP. The forum member claimed that users needed to add the value “EnableSuperfetch” to the Windows XP registry and then they would be good to go. He promised that it worked 100%, and said that he had tried it himself and all of his programs were now running more quickly. However, this was only a rumor, as there is no SuperFetch in Windows XP. Sharing this information did not do any good to other Windows users, but it also did not harm them either—it simply did nothing at all.

Myth generator: The Prefetch folder

There are a couple of myths involving Windows optimization that you should be very careful about. One of the most common revolves around Prefetch. A short explanation of what this feature does: Microsoft introduced Prefetch in Windows XP and subsequently integrated it into Vista and Windows 7. It memorizes data that a program loads into memory when it starts. For example, if you start Media Player, Windows accesses dozens of files to start the player. However, in most cases, it only needs some specific parts of those files. The Prefetch feature collects information about the files that are needed and in which order they should be loaded and stores it in the “Windows\Prefetch” folder. The next time you open Media Player, Windows preloads these recognized parts into memory before Media Player actually requests them—saving a lot of time! Prefetch does the same job on the entire Windows boot-up process, loading data in a more optimal fashion and decreasing boot-up time.

Example of a typical Prefetch folder

Dangerous myths: Deleting Prefetch folder

There are often claims that deleting the Prefetch folder actually results in less boot-up time and more free memory. The reasons for this vary—for example, some experts claim that Windows loads Prefetch information for all of the programs you’ve ever started on your computer into memory automatically, filling your RAM with unused data (this is not true.) These experts recommend deleting the contents of “Windows\Prefetch” on a regular basis, to keep your memory free from unused data. Ouch! Two reasons:

1. If you don’t run a program, Windows does not access the Prefetch information.
2. Windows maintains a maximum of 128 entries in the Prefetch folder. It cleans itself automatically.

So, if you actually delete the Prefetch folder, here’s what you should really expect to happen: Windows and applications will need noticeably more time to start, as the Prefetch data needs to be collected again. The entire performance of your system will slow down.

Let’s see for ourselves!

We benchmarked a Windows Vista system that had been running for months. The most used applications are Outlook 2007, Windows Media Center and Internet Explorer 8. We tested the boot-up performance as well as load times of these three applications before and after cleaning out the Prefetch folder.

As you can see, we experienced a noticeable slowdown during boot-up time. Vista also seemed to freeze momentarily at the logon screen, and all applications mentioned above took significantly longer to load.

Deleting the Prefetch folder is not the best idea

Stay away from the rumors and let Windows do the Prefetch job by itself. Otherwise, you’ll only end up slowing down your system, until the Prefetch feature is finished collecting all of the data it needs to speed up your PC again. Need more evidence? Check out this MSDN magazine article and blog post.