The background you see at the logon window is controlled by the LocalSystem account. This account has a profile that is loaded in the Registry by default. It's the .DEFAULT profile. (Note the dot at the beginning of the name.) This is not the same as the Default User profile .If you want to change the background, you can change the .DEFAULT profile to use a different bitmap. This requires hacking the Registry. Here's what to do:
1. Launch REGEDT32 or REGEDIT .
2. Drill down to HKEY_USERS | .DEFAULT | Control Panel | Desktop .
3. Find the Wallpaper value and change it to point at the location of the bitmap you want to use. You'll need to have the bitmap on the local machine. I recommend putting it in the %systemroot% directory along with the rest of the system bitmaps .
4. Find the TileWallpaper value and change it to 1. This will tile the bitmap, if you choose to do so. You'll need to tile if your bitmap is small because it will be hidden behind the logon windows .
5. Close the Registry editor .
6. Log off. The new bitmap should be there .
This was first published in April 2001