It is imperative that you keep Windows up to date and it does not happen automatically as there will sometimes be some optional updates that need to be done.
With Windows 8 there are 2 ways to access , check and update Windows.
The first is through the Control Panel , then find Windows Update
Or go to settings on the front screen , through the charms menu , then PC Settings , then update and recovery.
With Windows 7 to access Windows Update it is , Start , All Programs , Windows Update
Remember Windows Update is your first line of defence in computer security.