[deanhills]

• Windows Vista is one of the worst Windows versions that ever existed. Regardless of the service packs it has received. A overly annoying UAC and other things...

I remember many years ago when I first had to use Vista.  It was the worst of the worst OS, even in its "current" time.  The place where I was working skipped Vista to Windows 7 Professional.  And did its best to remove it from the few systems that had had Vista on it.  Worst part for me was its incompatibility with other systems and driver issues.

Windows 7 is dated, however what I can't understand is to use Vista when Windows 7 is available.  If there is something special in that generation of Windows that is needed over Windows 10, then Windows 7, and specifically Windows 7 Professional is so much better to use.

But OK back to the question of the OP, what security software to use.  I use Microsoft Security Essentials.  It's very easy to install, very light in using resources, and it works.  I find that most of the other better and more well known systems like Kaspersky are too heavy for Windows 7, probably because of Windows 10 definitions that aren't applicable to Windows 7.

So far Microsoft Security Essentials for Windows 7, is limited to definitions for Windows 7 OS, as after Windows 7, with Windows 8 and up, Microsoft is using different security software Windows Defender. So I hope to think that as long as Microsoft Security Solutions is still supported, its security software is better to use. It won't slow the system down.