If you share a Windows 8 PC with others and don't want them messing with the lock screen image, you can lock it so that it can't be changed. To do this, simply follow these steps:
1. Go to the Registry Editor and look for the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Personalization 2. If the Personalization key does not exist, right-click on the Windows key and select 'New->Key' and name it 'Personalization' 3. In the right pane, right-click and select 'New->DWORD Value' 4. Name the new value 'NoChangeingLockScreen' and set the value to '1' 5. Close the Registry Editor then click 'Yes' to allow the changes