Ok... I found a solution to this.....
In my case the duel monitor set up is one screen 1 = 1680x1050 and screen 2 = 1600x1200.....
So.... BOTH screens together = 3280x1280.....
BUT the desktop of the 1st screen has less height than the 2nd. The "active" area of the screen space as you can see it is the same dimensions of the screen... so I have made a image for you guys... where red is screen1 and blue is screen2 and green is an area of the bitmap NOT seen on the screen at all....
So all you need to do is fill in the RED and the BLUE areas and ignore the green, or even have stuff on green, just be aware you will not see it...
and load it up in backgrounds
Control Panel\All Control Panel Items\Personalization\Desktop Background Select
picture locations and select your desktop background directory... and then set it to
TILE now you will have a single image, shown on both screens, but as the image itself has 2 background, you get two backgrounds on each screen!!! No software needed!
Hope this helps!