A screen saver file will have the extension ".SCR" at the end of the file name. This extension is how the main screen saver executable in Windows recognises the file as a screen saver. The executable then reads the screen saver information in order to display the images that actually come across your screen. While there is only one executable process, the screen saver file itself is also an executable. When you first create or obtain a screen saver file with a ".SCR" extension, you will need to merge it into the screen saver component. The screen saver file can be installed as an ".EXE" without you having to change the actual extension.
Navigate to your saved ".SCR" file.
Right-click the ".SCR" file and click "Install."
Click "Yes" on the "User Account Control" dialogue. This will run the ".SCR" file as if it were an ".EXE" file. This triggers the screen saver file to be identified and added into the list of screen savers.