Most defiantly VSync. Or in-game Frame Cap. Turn off sync (via in game settings and/or nvidia control panel or and catalyst) . Or change frame cap limit:
C:\Documents and Settings\Your Name\Local Settings\Application Data\Activision\CoDWaW\players\profiles\Your Name\config_mp.cfg
Open it with Word Pad or note pad and change the setting to this:
com_maxfps 120
That said, depending on which COD, the folder may be different. Also, unless you have a monitor that refreshes more than 60hz (the standard), you will get screen tearing.