unable to install Nvidia drivers

what you are describing is an impossible situation,,if the original install was error free,,so it is recommended that you format your "C" partition and reinstall your os,it seems that something went south during the original install,,,
i have installed various versions of windoze so many times that i have lost track,and i can tell you that your situation can only be the result of a less than complete/proper install,,,however it came about,,,as for the driver version ,,the latest from the nvidia site,,,for your os and card should/will do the job "vga adapter" is just windoze saying that it has not loaded the drivers for it and is using the default windoze vga driver,,,BTW you could reinstall right over you current install before doing the reformat thing etc sometimes we get lucky sometimes not it's that damn registry once it gets a hold of something it keeps it,,and the only way to fix it,editing takes too long,is to reinstall,,faster in the long run .............