My vostro 200 on call of duty 4 runs slow !! I

Try lowering the screen resolution in the game settings also ste the grphics quality to low then see if the game is running fast if it runs fine then increase the graphics options one by one like resolution , bilinear or anisotropic filtering , antialiasing etc
and i would also like to tell you one thing that if the graphics card was inbuilt in your laptop then don't expect it to play heavy games like this you will have to install a separate graphics card to play good quality games