Microsoft Security Essentials is built into the 8.1 version of Defender, so you've got a free antivirus already. However I know the free version of AVG works, and I think most of the others do as well if you prefer to use them.
Good luck.
I have installed Malwarebytes which I used years ago and think it's a real good Malware/Spyware program. Now I need a real good free AV program. For what it's worth, I want a simple light resource program for 8.1. Thanks, Bill

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