The Show Desktop icon disappeared from Rusparadox's Quick Launch toolbar. He asked the Answer Line Forum how to get it back.
Once again, I have different directions for XP and Vista.
For Windows XP:
Select Start, Run. Type regsvr32 /n /i:u shell32.dll, and then press Enter. A little dialog box will tell you that the process succeeded.
Unfortunately, the icon still won't be in the toolbar. To put it back there, either reboot or perform the following simple steps: Select Start, Run, type "%appdata%\microsoft\internet explorer\quick launch" (include the quotes), and press Enter. This will bring up the contents of the Quick Launch bar as a folder. Drag the Show Desktop icon (which was re-created from that first command you tried) to the actual Quick Launch bar.
For Windows Vista:
Download ShowDesktop.zip from HowtoGeek.com (and thank you to those good geeks for showing me this trick). Open the zip file, and drag the only file in it to the Quick Launch bar.
Read the original forum discussion at http://forums.pcworld.com/message/168712.