Flight Simulator Screen Res ajustments problem

hi I am having a problem where there are infrequent times where the screen resilution ajustment tab will disappear as options as well as the 3D Video card settings that are avalible within FS FS will also fail to recognize my outboard video card , at present a new 7600 GS.This is not the first time i have had this issue, there were times when I was using my Radon 9600 PRO and it would behave the same way, the software that is. In the past if I tried, and I did this time, to reinstall, the driver for the card, it would remedy the issue, this time its being more fussy, not acknoleging the card, as it should.The only thing that i can see off the top, is re installing FS, but im sure thats not a long term, and may not help the problem.Thanks for any adviceZach Bender K7LTF