gfx_pixResWidth = 1920; (Set to your monitor's native width).
Open the folder where you extracted the files, locate , right-click it, and select Run as Administrator . serious sam 3 cannot set display mode
If you have a multi-monitor setup, a high-refresh-rate monitor (like 144Hz or 240Hz), or an ultrawide display, Serious Sam 3's engine might get confused. You can manually hardcode your monitor's exact specifications into the configuration file. gfx_pixResWidth = 1920; (Set to your monitor's native width)
Paste the following path and press Enter: C:\Program Files (x86)\Steam\userdata\ gfx_pixResWidth = 1920
This is the most reliable solution. By deleting the settings file, you force the game to forget its incorrect settings and redetect your monitor's capabilities on the next launch.