Security center is now Action center:
Searching for security center in windows 7, you would come up with nothing. All the items over here are shifted to Action Center. Not sure why they did that, but security center was better
User Access control:
UAC has four stages. Each stage has option to configure the level of security. You would find a picture below.
We could ourselves configure if we need that annoying screen asking for permission to come up each time or not.