I installed the latest drivers last night from nvidia, so yeah I guess so
What I mean by a fresh install is theres actually a option when you install the drivers, that says "preform clean install" it will remove any previous drivers you had before and practically install everything all over again like it was never there. If you just updated the drivers and never uninstalled them, that could be a problem. But if I'm not mistaken I believe COD4 is a lot more CPU intensive than GPU, so I dont think the GPU could be at fault.
Right, Some jumps on cod4 require a higher FPS so that you can jump further and move around the map faster. So I do need to have that higher FPS for advantage whilst playing, Yes I may not be able to see the change in quality but the FPS advantage on COD4 is crucial to how a player plays at LAN events etc... I got more fps with my 450 and than the 660 Ti