Force a Video Mode
Follow these instructions to configure your video mode and resolution before launching a game:
Important:
If you are forcing a refresh rate on your system (this is not recommended), you will need to ensure that you specify the forced refresh rate in the launch options.
Open Steam
Go to the "Library"
Right-click the game which needs to be reconfigured
Select "Properties" from the menu
Click the "Set launch options..." button
Remove any launch options currently shown.
Type -gl in the box.
Specify the appropriate Video Mode and Video Option switches from the lists below
Video Mode Launch Options
Use the -w # switch (where " # " is a number from the list below) to specify the display resolution:
640 (640x480) GoldSource Only
720 (720x576)
800 (800x600)
1024 (1024x768) - This mode offers the best performance for most cards
1152 (1152x864)
1280 (1280x1024) - This mode is optimal for high-end cards
1600 (1600x1200) - This mode requires a high-end monitor and a high-performance card