Go to this youtube video
COD4 Get High FPS on any Computer. - YouTube
it increased my fps by 2-5
also try this:
type in the command
NOTE:This will change your controls so before entering this, Remember the default controls
For you lazy People out there here are the controls for moving and other stuff
Jumping Over Things=Space
Prone(go on the floor)=Ctrl
Aim down sight=Right Click
also your FPS Counter and Lagometer should appear so to make it disappear just type in
/seta cg_debugInfoCornerOffset "0 0"
Also try lowering your Resoultion to the Resoultion Your Graphics card has(yes i know its suppose to be to lower into the lowest it can go)
post if it helped!!
also i know some of you might say to also put gamebooster but acutally gamebooster does give more fps but it makes you lag more and your ping go high