Resolved Windows Defender Updates Query

Since you have MSE (Microsoft Security Essentials) installed on your Windows 7 machine, MSE turns off Windows Defender because MSE has Windows Defender built in.

At least that's the way I understand it.

I have Defender installed on my Windows 7 setup, and it is still active, but I have Avast for an antivirus program.

 

Use only one anti virus program at a time. Most of the av programs disable Defender otherwise you can do it yourself.

As a second line of defense, use Malwarebyte's Anti malware. Scan your computer manually once a week & everything should be ok.