Instructions
Navigate to the Fraps website (fraps.com) and download the latest version of the software. The free version of Fraps is limited to recording videos of only 30 seconds in length, but still has full benchmarking capabilities.
Install the Fraps software and run it. Click the "General" tab at the top of the program screen and uncheck the box next to "Run Fraps when Windows starts."
Click the "FPS" tab at the top of the program screen then select the folder where you want the benchmarks and benchmarking hotkey to be stored. Click the "Movies" and "Screenshots" tabs and set up the folders and hotkeys to your liking as well.
Exit Fraps and then start Steam. Log into your Steam account then click the "Add a game" button on the bottom left of the screen. Select the "Add a non-Steam game" from the menu that appears.
Select "Fraps" from the list of installed programs then click "Add selected programs." Fraps will then be put in Steam as part of your game library. Click on the "Fraps" icon in Steam then click "Play" to activate it. Click on the game you want to benchmark and then click "Play" to run it while Fraps is running in the background through Steam.