I think Windows Defender started with Vista - and supports every operating system since. It's on my Windows 7 computer.

Windows Defender on versions previous to Windows 8 was more of an anti-spam program. Starting with Windows 8, it was a full-fledged anti-virus program, albeit not a very good one. It replaced the old Microsoft Security Essentials. It has slowly been improved greatly, but I'm not sure where it stands with the paid anti-virus programs now. It used to rank towards the middle or lower. I really like using it with Malwarebytes Pro.

Thanks for that info, Marian and Draclvr

EDIT :

My Son in Law kindly checked the registry on my Win7 machine for me, and, as we both fully expected, there were no aliens present !!

I have every confidence in my "Norton and Malwarebytes" security combination

Well reading through this thread again, no one actually seems to have suffered a successful attack

So far, so good anyway! That's always good news!