If all these ways can't work, the easiest way you can see.
--- How to start/enable security center
1.Click Start, right click on Computer and select Manage.
2.Click on Service and Applications > Service on the left side.
3.Find the Security Center on the right side, right click on it to start.
1.First of all click the Start button to view the Start Menu. Then choose the Control Panel option.
2.After click Control Panel, enter into System and Security, then click into Windows Update.
3. Now you are at the Windows Update section of our Window 7 Control panel. You can manually look up for any new updates by clicking the Check for updates button