Open your registry and find the key below. 

Change the value of 'ScreenSaveActive' to '0' to disable the screen saver. 

Restart Windows for the change to take effect. 

Note: An alternative screen saver can be used, if disabling is not an option, simple change the value of 'SCRNSAVE.EXE' in the same to key, to equal the full path of the screen saver you wish to use. 

Key:[HKEY_USERS\.DEFAULT\Control Panel\Desktop]
Value Name: ScreenSaveActive
Data Type: REG_SZ
Data:(0 = disabled, 1 =enabled)

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