My Show Desktop Icon no longer works in Windows XP Pro.  I followed these steps to try to fix the problem (deleting the "broken" shortcut first):

1. Click Start, point to All Programs, Accessories, and click Note pad.
2. Type in the following:
[Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
3. Save the new file as Show Desktop.scf in the Windows\System32 directory.
4. Open Windows Explorer.
5. Browse to the Windows\System32 directory and locate the Show Desktop icon.
6. Click the icon and drag it onto the quick launch bar.
The Show Desktop icon should now be available again on the quick launch bar.

After these steps, I again have a Show Desktop icon on the Quick Launch Bar, but it still doesn't work.

I have been using A1PC Cleaner, RegVac, and Speed Startup but I don't know if any of these programs caused the problem.

Any help will be appreciated.  Thanks!

I don't know about that.  I have not heard of any of our programs causing anything like that.

I also had that problem. I solved it by info from "LockerGnome" article by Brian.

Here is how you can fix your computer.
1.     Go to Start | Programs | Accessories | Notepad.
2.     In a blank text document, type:
[Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
3.     When you save the text document, you need to change the "Save as Type" field to "All Files," and type "Show Desktop.scf" (sans quotes) for the file name. You'll want to save file in C:\Windows\System or C:\Winnt\system32, depending on your Windows installation.
4.     Use Windows Explorer or My Computer to navigate to where you saved the Show Desktop.scf file.
5.     Now, right-click the file and choose "Create Shortcut."
6.     Move the shortcut to C:\Windows\Application Data\Microsoft\Internet Explorer\Quick Launch if you are on Windows 9x, C:\Winnt\System32 if you are on Windows NT4/2000, or to C:\WINDOWS\System32\Config\Systemprofile\Application Data\Microsoft\Internet Explorer\Quick Launch for Windows XP.
7.     Last, you need to right-click the shortcut, choose Rename and type "Desktop" (sans quotes) for the name.
Now the Show Desktop icon will automatically appear in the Quick Launch toolbar, and you shouldn't have to restart. However, if you don't see the shortcut, then try restarting your machine before retrying the steps.

Pay special attention to steps 3 and 6.   Hope this helps.

jeflcon

Thanks, jeflcon, for taking the time to recommend a possible solution.  I tried the steps twice with no improvement.  I re-started my computer when the Show Desktop icon didsn't appear in the Quick Launch toolbar after following the instructions carefully but the icon still didn't appear.  I don't know what caused this problem or what the solution is (if any.)  So I will just keep using the Windows Key/D method.