Right-click your Windows desktop and select . Scroll down and click on Advanced display . Locate the Refresh rate drop-down menu. Temporarily lower it to 60 Hz .

Stay on the tab and locate the Launch Options text box at the bottom. Type or paste the following exact command: +g_bFullscreen 0 Close the window and launch the game.

If you'd like, I can (like "DirectX Error" or low FPS).

Find the following lines and change them to safe values (e.g., 1024 × 768 or your native screen resolution): gfx_iScreenHeight = 1080 (or 768) gfx_iScreenWidth = 1920 (or 1024)

Navigate back to your Serious Sam 3 userdata directory: ...\userdata\[YourUserID]\41070\local\SeriousSam3\ Delete the folder entirely. Delete the Caches folder if it exists.

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Alternatively, you can right-click the file, open it with Notepad, search for the lines g_bFullScreen and pixSizeX / pixSizeY , and manually change them to match your current desktop monitor specifications. Method 3: Reset GPU Scaling and Monitor Refresh Rates

For systems using modern integrated graphics or multi-monitor high-DPI displays, the legacy Direct3D calls might fail entirely. Wrapping the engine calls into modern APIs resolves this issue.

Save the file ( Ctrl + S ) and close Notepad, then launch the game. 3. Clear the Shader Cache and Temp Files

If forcing the resolution through Steam does not work, the game's local configuration file might be corrupted. Deleting this file forces Serious Sam 3 to generate a brand-new file with default settings upon the next boot.