Once you install and run the program, open the ‘User Whitelist’ and add “HL”. This tells the program that the “HL.exe” is one to look for. Be sure to save. Next, click on ‘Edit Settings’ in which you’ll need to add your monitor’s native resolution after the presentWidth and presentHeight variables. Again, save and close.
From there, make sure the tool is activated, run the game, head to the options, and make sure the game is enabled to run in widescreen. Missing this step means that GeDoSaTo’s downsampling resolutions won’t be listed in the graphical options.