It is easy to do and easy to fix...so this is two pranks in one!
Step 1: Get a PRT SCR...
Start he Paint application (can be found by going to START then All Programs, Accessories and then Paint). Click EDIT and then Paste. This will take the image you just took of the desktop and place it into the Paint application.
Click on FILE and SAVE - name the file something easy and note the file path. It is easiest to save it to the desktop or the users Pictures directory. Close Paint.
Step 2: Remove the Desktop Icons...
Now you need to remove the icons from the Desktop.
Right Click any blank space on the Desktop, click VIEW and then remove the checkmark from the "Show Desktop Icons" by clicking it. The icons will disapper shortly.
Right Click any blank space on the Desktop, click "Arrange Icons By" and then remove the checkmark from "Show Desktop Icons" by clicking it. The icons will disappear shortly.
Step 3: Change the Desktop Wallpaper
Now that you have a desktop with no icons, you need to load the image that has icons as the wallpaper.
Right click the desktop and click PERSONALIZE. Choose Desktop Background and then browse for the image you created in step one. Click OK to apply the image to the background.
Right click the desktop, click PROPERTIES. Click the DESKTOP tab and then the BROWSE button to find the image. Select the "Stretch" option for the Position and then OK to apply the background.
Step 4: Sit Back and Watch the Fun...
Now you get to watch the victim frantically click on the "icons" and have absolutely nothing happen.
If you are really clever, you can undo this, show them that the comptuer is working and, when they are not looking, set it up again to continue the fun...
This is a classic trick that works on all versions of Windows - so have fun with it!