The specifics would depend on your Windows version, but going by Windows 7 (which should be reasonably useful in the absence of a specified version, and which I have easy access to):
- right-click on the desktop and pick Personalize
- click Desktop Background
- right-click on the selected image and either:
- pick Properties and look under General, Location
- or, pick something under Open With
This should provide you access to the file so that you can copy or save it elsewhere. I would guess that it is stored in a temporary files folder somewhere currently.
Possible duplicate of Where does Windows store its wallpapers?, How can I find the file that is currently used as a wallpaper in Windows 7?, Custom Windows 7 wallpapers location, How could I find out the path to the current desktop image, for Windows 8 ...
– Karan – 2013-07-18T01:05:12.783