i'm a first time 'SuperUser' poster .. what i want is to programatically change Desktop Wallpaper every few hours .. i'm using a batch file (.bat) and don't want to use other languages or programs, just the pre-installed stuffs with Windows XP .. i've already made my script that will modify values in the Registry

reg add "HKCU\Control Panel\Desktop" /v Wallpaper /d "C:\Pictures\picture1.jpg"

but it's not taking effect real time even with this command:

RUNDLL32.EXE USER32.DLL,UpdatePerUserSystemParameters ,1 ,True

need to reboot first to take effect.

if i'm going to use Display Properties, it'll show at once. what i've noticed is that changes will take effect real time if it's a .bmp file and not for .jpg images.

Second option is to convert JPG to 24-bit BMP files (to look exactly the same, but will triple the file size), but i'm hoping a better way ..

i've already googled things but no avail.. i hope you (the helpful reader) can post any .bat or even vbs script to change Desktop Wallpaper instantly with JPG pictures .. hoping there's an answer without installing other apps or scripts ..