>(nRetval=21)
>More progress...
>And now ?

Okay, good, that function is working as expected. Now try:

declare integer GetDesktopWindow in win32api
? GetDesktopWindow()

I usually get 128 for this. If this works, try the entire thing again, or if you want try using the value you get for GetDesktopWindow() as the first paramter int the PrintWindow call. I'm still wondering if you have all the letter cases exactly right, they have to be perfect, or things won't work right...