What I wanted is to make sure you had run the evaluation, since it effects how Windows treats your video.
My system that has an onboard graphics seems to be close to your readouts, and the driver you are running, as you stated, is up to date.
So what else might it be? If for some reason you were running different codecs, might effect the performance. The fact the Windows 7 drivers were not good for you card would certainly mess up your system...
I can't remember which ones, but some Nvidia cards seemed to have problems with Windows 7 just after the release, but by now, certainly this was corrected. But you might check to see if you can find anything about Windows 7 and your particular card.
Do you have another card you can...