Through windows update ? Weird, I have checked with mine and there is no update for intel... I'm still with the first version of the drivers (march)
I believe you will need to install the 3960 first (by uninstalling the March HD5000 driver from device managerm reboot, then install the new HD5000 driver downloaded from Intel, reboot).
Then you should be able to see an Optional update called Intel WDDM something, which is around 80 MB in the Windows update. Do that update ONLY, then reboot, you will see the 3977 driver.
I personally did those and can confirm it works. Hope this helps.