fraps is not the only way if you use source recorder, what you have to do is record a demo by typing inconsole record and then the name you want for the demo. then type stop when you have finished recording. then you have to type startmovie moviename avi (note this will disconnect you from the server you are in), by typing this a small box will appear asking you what codec you want to use, i normally use HD fine pic .
Then in console type playdemo and then the name of your d emo
NOTE THIS WILL BE REALLY LAGGY AND THERE MAY NOT BE ANY SOUND
then when the demo has finished just type endmovie and the file will be in the cstrike directory of steam.