When you setup a background wallpaper for your desktop, the initial logon screen wallpaper is not changed and stays as the default Windows appearance. This tweak allows you to change the default wallpaper.

1. Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
    
2. Expand HKEY_USERS\.DEFAULT\Control Panel\Desktop (see picture 1).
   
   

   Picture 1

3. Modify the value of "Wallpaper" to equal the path and filename of the bitmap (BMP) file you want to use as the background (e.g. 'c:\windows\mylogo.bmp').
    
4. In the same key, you can also modify these additional values "Pattern" and "TileWallpaper" to set the background pattern and Tile mode respectively.
    
5. The modifications you made will be in effect after you reboot your PC.