Windows – How to change the order of extended displays

In my experience, there does not appear to be any native means of resolving this. Windows will assume that any wallpaper image intended to span multiple screens should originate from the top-left corner of the primary display, regardless of where the primary display is in relation to the others.

There are a couple ways to work around this. One, as suggested by @Petr, is to chop up the image in an image editor (e.g.: MSPAINT) and put the right half on the left and vice-versa. This can be a little tricky, especially if the image isn't at the same aspect ratio as your monitor or if you have monitors with different resolutions/ratios.

The other alternative is to get a program that will do it for you. There are several out there which will generate the image for you to set as your desktop background. I prefer DisplayFusion, which also offers a number of options for resolving other common multi-monitor headaches. DisplayFusion comes in Free and Pro editions, and the Free edition is totally free - no adware, spyware, or nagware.

Right-click on the desktop, choose Screen Resolution option, rearrange monitors in the display.