Introduction

There are a surprising number of sites out there that talk about setting up multimonitor displays in Windows. Most say you're stuck having the same wallpaper on all monitors. If you try to center a bitmap, it centers it on each display. If you tile it, it is tiled separately on each display respective to that display's top-left corner. If you stretch it, it is stretched to fit each separate display.

 

The Short Answer

So, you have multiple monitors and you want your wallpaper stretched across all of them. First, you need to have Active Desktop enabled (this is automatic in Windows XP). If your left-most monitor is your primary display, you're in luck. All you have to do is select the wallpaper you want in Display Properties and choose "Tile" for the position. Tiled wallpaper is of course intended to be used with a repeating pattern across your desktop, but it just so happens that with Active Desktop enabled, the wallpaper will be wrapped around your entire multimonitor desktop starting at the top-left corner of your primary display. Conveniently enough, this is exactly what you want if your primary display is on the left.

 

The Long Answer

Most people who have more than two monitors aren't going to have the primary display on the left. It's still fairly simple to get your wallpaper the way you want it. You just have to make your wallpaper the background of an HTML document.

More specifically...

  1. Make a BMP or JPG image that is the full size of your entire desktop.
  2. Create a new text document in your "C:\Windows\Web\Wallpaper\" directory with the line: 
    <HTML><BODY BACKGROUND="D:\DESKWIDE.BMP"></BODY></HTML>
    (replace "D:\DESKWIDE.BMP" with the image name)

  3. Rename the file to "Desktop.html" .
  4. Go to Display Properties and select "Desktop" as your background.
If you later add things to your Active Desktop HTML, the HTML will be justified with respect to the primary display, but the background is always shown accross your entire extended desktop.
There are two good ways to organize your wide wallpapers. First, you can use the above method and change your wallpaper by copying a different image on top of of "D:\DESKWIDE.BMP" (or whatever you called it). This is the best method if you like to actually use Active Desktop to put cool HTML stuff onto your desktop because you keep a single source HTML file for your desktop. Otherwise, if you like to keep several different wallpapers easily available, you can make copies of Desktop.html with different names and have each of them point to a different bitmap in your "C:\Windows\Web\Wallpaper\" directory. Then you can select different wallpapers from Display Properties just as easily as if they were bitmaps you had dumped in your Windows directory. If you have a lot of different wallpapers around, though, there's another method you might prefer...
 

Modified Wallpaper

Simply modify your wallpaper image to compensate for the way "Tile" works. For example, if your monitors are setup like this, with #1 being primary:

Then you cut/paste things around in Photoshop (or MS Paint, GIMP, etc.) to look like this:
Then all you have to do is put the modified images in your C:\WINDOWS\Web\Wallpaper directory.

Hope this helps!