can't figure this out. two systems (pro 64bit). one was upgraded from win7 64bit, other was fresh install. I can change the lock screen image fine for the freshly installed win8. However, doesn't matter what I do for the win7 upgraded system. It will not change the lock screen image and sticks to the default. I can change everything else fine (start image, pattern, color etc). I've taken ownership of the C:\ProgramData\Microsoft\Windows\SystemData\S-1-5-18\ReadOnly\LockScreen_Z\ folder and replaced the LockScreen___1920_1080 image there with one of the other C:\Windows\Web\Screen. No dice. Once replaced, all I get is the plain blue background color on the lock screen - no image. any hints? thanks folks