I'm not sure whats happened then. I would uninstall all versions of COD4 then make sure all the program folders are empty or deleted. Make sure there is no trace of it left on your PC. Then do a fresh installation. Install it, make sure single player works with NO patches. Then, install the 1.6 update, then the 1.6>1.7 update. Then, when you start COD multiplayer on the main screen it should read 1.7.568 in the bottom right hand corner.