Looks like you may need to boot the computer into safe mode and then remove the windows update. Seems as if something towards the end of the update went wrong. To put your machine into safemode, turn it on and immediately hit F8. This will bring up a boot menu and you can select "Safe Mode with Networking." Once the computer boots, you can go to the app called Update and Security. Look for an option named Recovery and select "Go back to a Previous Version of Windows." Should take about 30 minutes total.