Thank you for the response to my request. I have made the changes you suggested and I am still getting the error dialogs. Here is the code segment
echo "Start of Wallpaper change"
REG ADD "HKCU\Control Panel\Desktop" /v Wallpaper /t REG_SZ /d "U:\Azul.bmp" /f
REM The following line refreshes the desktop.
When you say it doesn't work on 7 do you mean it gives you an error, or does not have the intended effect? It runs on my Windows 7 machine just fine, however I'm not trying to mess with the wallpaper to test if it actually functions.