Instructions
Load "Left 4 Dead 2" and open the graphics options from the main menu. Turn down shading options and texture details and turn off multicore rendering.
Update your graphics card driver to ensure optimal performance. Check which graphics card you have by clicking on the "Start" menu, opening the "Control Panel" and clicking on "Device Manager." Go to the identified graphics card's website and download the latest drivers for your card.
Run "Disk Check" to check for any errors on your computer and clean them up. Open the Start menu and click on Computer, right click on the drive you want to check (the one "Left 4 Dead 2" is installed on) and click "Properties." Click on the "Tools" tab and click the "Check Now" button.
Run a disc defragment for your hard drive to clear up hard drive space and reorganize your files.
Delete old files and uninstall old programs that you are not using any more. Games run better when there is more hard drive space available. Click on the "Start" menu and select "Control Panel," then go to "Add or Remove Programs" to uninstall unused programs.
Disable processes that are running in the background. Open the "Task Manager" and click on "Processes" to see all the programs running on your computer. Right click on the process you want to end and click "End Process."