You may be using a shared pc, but you don’t want anyone to change its screensaver. You want something which will disable this feature. Well the bellow steps will make it possible.

1. Open RUN box by pressing Win key + R.
2. Type Regedit to enter the registry.
3. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
4. Now on the right pane right click and select DWORD (32 Bit) value and rename it as NoDispScrSavPage.
   
5. Double click on that (NoDispScrSavPage) and change the value data field value to 1.
6. Close registry editor and check your screensaver setting (right click on desktop – select personalize) you will find Screensaver option disabled. (see image below)

Hope this helped, do comment. 🙂