windows defender is off windows essentials is on?

windows 7 IE 11 , why does my security say windows defender not turned on , yet my antivirus windows essentials says full protection on and my firewall check is on .everything is running OK how ever On another computer both defender and essentials are on with Vista
  

If you are able to remove Microsoft Security Essentials in the Control Panel > Add or Remove Programs (Programs and Features)... you should be able to use Windows Defender.

If you change your mind later on and want Microsoft Security Essentials to be active, simply re-install MSE, click your choices within the MSE menu, for sure, after a Restart, Windows Defender will [again] be turned off.
Otherwise, follow Master's advice and you should be just fine.