It shows a message

i placed everything in the cod4 folder and it did not work

Did you try and run it from within the cod4x_client_21.1 folder?

and where your iw3mp.exe file?

here it is

yes i did for one time untill i saw the error and put everything in the cod4x folder to the cod files

iw3sp.exe is the single player exe. You are missing iw3mp.exe for multiplayer