Windows 7 dual monitor wallpaper tiles in the wrong direction

The other day I got sucked in by Lifehacker's Wallpaper Wednesday. One thing led to another and I downloaded a relaxing lake scene that would stretch across my two 23" monitors.

However, once I selected my new desktop image I noticed a problem. See the majestic trees on the left monitor? They're supposed to be on the far right of the right monitor, which is also the main display monitor. This is certainly a problem.

I futilely tried altering the monitor configuration in 'Control Panel\Appearance and Personalization\Display\Screen Resolution' but that never got the results that I wanted. Updated display drivers in case there was a software solution but that didn't solve the problem either.

I knew that my monitor-spanning image's 'Picture position' had to be set to tile in 'Control Panel\Appearance and Personalization\Personalization\Desktop Background' so I did some searching using terms such as 'tiling wrong way' and tiling 'right to left' and eventually came across a post like this one that revealed the underlying issue: Windows starts drawing the image in the top left of the primary display then wraps to the other displays.

With this knowledge I realized that I was going to have to use Paint.Net to resolve the matter.

The first step was to break up my 3840 x 1080 image into two equal distinct images. Following these steps from the Paint.Net forum I was able to produce two 1920 x 1080 images.

1. Open original source image
2. Click on Image > Canvas Size
3. Uncheck Maintain aspect ratio CheckBox
4. Set pixel size to 1920 width, leaving height as is
5. Set Anchor to Top Left
6. Save this half of the photo, naming 'left', '1', or whatever you choose
7. Click undo, to undo the canvas size and repeat for the right half or reopening the source image and repeat, using 'Top Right' for step 5

Now I had to combine the two images produced above into a new 3840 x 1080 image. Again, the Paint.Net forum had the answers.

1. Open the image that you want to appear on the left monitor first
2. Image > Canvas Size
3. Uncheck Maintain aspect ratio CheckBox
4. Set Anchor to Top Right
5. Double the width (in my case I changed 1920 to 3840)
6. Import the image that you want to appear on the right monitor by using Layers > Import From File (by default this image's anchor is top left
7. Save this new file

Did it work?

Yes.

Clearly this solution is not applicable to all monitor configurations, but it should give you an idea of how to solve this problem.