Star Wars Knights of the Old Republic II: The Sith Lords

Ok so iv installed the game with no problems, however when ever i try to play the game it tells me that my video card drivers are out of date. the exact message i get in the detail report is "Your current video card drivers are out of date NVidia requires Detonator 45.23 or better" i do not know what this means but i wnt onto the Nvidia website and downloaded the updates for my "GeForce 8400 GS" video card, however when i did this it messed my computre up every time i would get a message on screen sayin not optium settng recommed 1440 x 90 60 mode, i do not no waht that means ither but my computre would reject my montor in this state and i would have to syteme wipe and recover my computre to solve it, what can i do other than go and buy a new video card??? please help