Changing XP Background (Wallpaper) Images

I know, I know, XP's old.  But this is Practical School Tech and education is a little behind the times.

We had a couple of student systems where the students had set a background image by right-clicking images in IE and setting them as the wallpaper.  Cute trick, right? But it's a pain to undo on a system where they don't get rights to the Display Properties page.  The setting is stored per user (that way everyone can have their own) which is great unless your using a generic account that several students share.  So how to undo it?

I though I'd start with the background image file.  I did some Googling and most places said look in here 
C:\Documents and Settings\Local Settings\Application Data\Microsoft\

But that isn't the right path, but it's close, it's really in
 C:\Documents and Settings\Application Data\Microsoft\Internet Explorer

Or if you want to find it in a batch file (or just typing by hand), try this path instead
%AppData%\Microsoft\Internet Explorer

After finding the file I wanted to know where it is set in the registry.  Since the image was set from inside IE file name was a very descriptive Internet Explorer Wallpaper.bmp.  That's fairly unique, so I just searched through the registry for that file name.  It turns out that path is stored in
HKEY_CURRENT_USER\Control Panel\Desktop

To clear the background image out I just blanked out the registry here.
HKEY_CURRENT_USER\Control Panel\Desktop\Wallpaper  

After a reboot (or log off and log back on) the background image will be cleared and you'll be back to the pleasant soft blue.  

But I didn't want to stop there.  I wanted the change to go into affect immediately. I new when I changed the background through the Display Properties that the change happened right then.  So that means there's a programmatic call somewhere that can make that happen.  I had figured it was probably in some windows dll file and since wallpapers had been around so long that it was probably in one of the more common ones.  A little more Googling and I came across this line

%SystemRoot%\System32\RUNDLL32.EXE user32.dll,UpdatePerUserSystemParameters

I crossed my fingers and gave it a shot and what do you know, it actually worked.

So I take all this information and roll it into a ZENworks bundle that deletes the key and then calls the UpdatePerUserSystemParameters to make it go into affect immediately.