For those that are stuck in full screen, that's how to solve it:
1st: Go to "C:\users\%username%\Documents\My Games\Super CRT Sim\Config"
(where %username% is your username).
2nd: Open the "Config.ini" file.
3rd: Search for these lines:
Fullscreen: true
FullscreenWindowed: false
and change them to
Fullscreen: false
FullscreenWindowed: true
4th: Save the file and close it.
5th: Open the program again. It should open in windowed mode now.