Please provide details on what you mean. No Desktop is rather bland.
Does the machine give an error? Is it powered on? did a meteor stike your house and incinerate the desktop upon which sat you computer?
without details, were blind...
Sometimes, computers get some "kinks." Sometimes when you restart your computer, the "kink" will be gone. Did you try to reboot? I can't really think of anything else because like Inaris said, we need more details.
All you had to do was hit CTRL-SHIFT-ESC, go to file, then "New Task (run)" then browse to your "windows folder" and open up "explorer.exe". There is another way but i have forgotten where it is located in the registry. This way is a gr8 prank as well to play on your friends. You can use it to, turn their computer into a word processor! lol PM me for more information.