Kapersky has topped the recommendations by the mag Computer Active for the past three years. I've just installed it on desktop and 2 laptops, and it seems fine.
Windows 8.1 has security built in in the form of Windows Defender, which is at least as good as most of the alternatives, is light weight and unintrusive.
I have Windows 8 and the only antivirus I've downloaded is Baidu Antivirus. I've had no problems with it and it helps with system repair and improving my computer speed.
I have tried several antivirus software includes avg, avast & eset but now i am stick with Comodo Internet security suits which available for free. Reason for choosing this products is it is free, full protection with auto sandboxing technology, it has memory firewall and much more. Get more details about this products at https://www.comodo.com/home/internet-security/free-internet-security.php