At first i thought that you have too many processes or too many programs running, but that would affect your 2d games and movie playing also. But give it a try anyways, push ctrl+alt+del and go to processes, now look up each of the processes' name and google them, see if they are needed or not. If they are needed, leave them alone, if they aren't needed, then end them.
Before playing cs, i usually end all the unnecessary processes so i wont have any problem while getting my m-m-m-monster kills
If it doesnt work, ill try to find out something else.