I assume (dangerous thing to do ) that you are talking about a Boot Camp update that is triggered through the Windows' Apple Update.
One thing is that I do not know what is in the Apple update, what I do know from Boot Camp 3.0 is that Apple does not uninstall under windows previous drivers and it just adds new drivers to the mix. When I installed next Boot Camp 4.0 and all the 3.0 drivers were still in Windows I had nothing but trouble and it got resolved by a new install. (which I hasten to say was required anyway because of replacing the internal HDD with an Intel X25M G2 80 Gb SSD)
What I am doing - and have been doing for the past 9 ~ 10 years - is when I need to install anything in windows to do this using "Total Uninstall 5". This makes a system snapshot prior to install and afterwards. Then when uninstalling it tidies up all the remnants left behind in registry etc. Saved me many a time to have to backtrack (restore from backup) or re-install.
Getting back to your predicament: if there are gfx drivers in the Apple update and they are a newer version than the ones that you have then Windows will use those. Sometimes you might be able to manually force Windows to use the old version but not always garanteed.