Think of this as the 21st Century equivalent of the “boss key.” When you hear footsteps and you want to clear the contents of the screen right now, hold down the Windows logo key and tap L. In Windows XP, that shortcut takes you to the logon screen if you have Fast User Switching enabled. If you log on to a Windows domain server on a corporate network, or if you’ve disabled Fast User Switching, or if you’re using Windows 2000, the Windows logo+L shortcut locks the computer, displaying a logon dialog box that doesn’t go away until you enter your password.

Updated 25-May-2005: Finally! Some authoritative input on this issue! Ryan Myers, a developer on Microsoft’s Windows Client Performance Team, wrote a very informative blog post, “Misinformation and the Prefetch Flag,” that clears up several of these issues. I’ve revised some remarks below in accordance with his entry.

In today’s tip of the day, I warned about following advice from so-called Windows experts who don’t really know their stuff. Case in point: the thousands of Web sites that pass along the bogus advice to clean out your Prefetch folder. (No! Don’t do it!)

A commenter who read that tip asked a great question:

What do you think about adding /prefetch:1 to shortcuts? Does it make any difference? I’ve read on several forums to use the switch for quicker application launches but I haven’t really noticed any increase in speed.

I’d never heard of this tweak, so I did a Google search for prefetch switch program shortcuts and found more than 10,000 Web pages that advise making this speedup tweak. In the rest of this post, I explain why they’re all wrong.

Continue reading “Debunking yet another bogus Windows tip” →

At least once a week I run across some well-meaning soul who passes along a dubious tip designed to enhance the performance of Windows XP. According to these folks, you should clean out the Windows Prefetch folder regularly to improve your system’s performance. They’re wrong, because they don’t understand how this feature works. Even generally reliable sources like Fred Langa can get tripped up. Here’s what you need to know:

The Prefetch folder is not a cache – at least not in the sense that you normally think of when you use that term. This folder contains trace files and layout files that Windows uses in specific circumstances. Trace files describe the exact order in which segments of programs (executable files and dynamic link libraries, including those that make up Windows itself) load. Windows uses this information to launch Windows and Windows programs in the most efficient way possible. Layout files provide a list of files and directories in the order that they are accessed when you start your computer or run a program. The Windows XP Defrag program uses the layout information to arrange these files in a contiguous region of the hard drive. The “prefetching” doesn’t mean that code is being loaded unnecessarily; it means that code is being loaded in the right way, and only when it’s needed.

Cleaning out the Prefetch folder will not improve performance. I have proved this with a stopwatch repeatedly on multiple test systems, and documented the results in Windows XP Inside Out Second Edition. In fact, emptying the Prefetch folder will actually reduce performance, because Windows has to re-create the trace files the next time you run the program. Windows cleans out old files here automatically, and it uses the current information simply as instructions to help load programs more efficiently. If you delete a program, its layout and trace files go unused and are deleted within weeks.

This isn’t the first time I’ve written about the Prefetch folder. I have a detailed write-up on the subject here. Be sure to follow the links to the excellent article by Mark Russinovitch and David Solomon and scroll down to the section entitled Prefetch, which explains how this feature works in very clear detail.

The next time someone tells you that cleaning out the Prefetch folder is a performance-enhancing measure, tell them it just isn’t so.

Normally, when you open Windows Explorer, the window opens in your My Documents folder, with all other drives and folders visible in the Folders pane on the left. But if you just want to work with the files in a single folder (with all its subfolders), don’t forget the trick of creating a “rooted” Explorer window that contains only the specified folder and its subfolders. The secret is using the right switches after the explorer.exe command – in this case, /e to open an Exporer window (with folders visible) and /root to restrict the display of folders to only those that are below the folder you specify.

This shortcut, for instance:

%windir%\explorer.exe /e,/root,%userprofile%\My Documents\

shows a “rooted” view of the current user’s My Documents folder.

Try this one to open the Shared Documents folder:

%windir%\explorer.exe /e,/root,%allusersprofile%\Documents

Note in all cases that there is a space after the explorer.exe command but no space between switches and parameters.

Both of these shortcuts take advantage of environment variables. These systemwide shortcuts, identified by the percent signs on either side of the variable name, automatically point to the correct location, based on the current user profile. If you create one of these shortcuts and put it in the Desktop folder in the All Users profile, the shortcut will appear on the desktop of any user and will open properly for each logged-on user, without requiring any customization.