Are you logged in with the same Microsoft ID and have you got settings set up to share your settings across all your logons so then it looks familiar wherever you log in?
To me it looks like your attempted install of Windows on the desktop has not worked for some reason. Did you perform a clean install of Windows or try to activate the test system with your key? The latter is not recommend and has caused problems for a number of buyers. Where did you source your Windows key? If you got it very cheap online, then it is almost certainly a bogus key and that is another potential source of your problems.
That hasn't been clean installed, or it's been logged in with an account that was previously used on a PCS test windows and has therefor synced the desktop background.