I'm helping a friend bring a refurbished Win 7 up to speed. I suspect Microsoft Security was removed by the former owner because we can't find it. We are corresponding by Skype so I can't actually touch her computer.  I do my work on Win 8.1, where this post is coming from, so I can't do experiments on my machine to see what she can do.

We can't find the Microsoft Security program in her list of programs.  I'm not sure what it is called on Win 7. 

Is it Microsoft Security Essentials, or Windows Defender, or what? 

Whatever its name is, is it free for Win 7, or will she have to pay?

Please give us a URL for where we can download the appropriate version for Win 7.