What Starcom said... if you got Windows 8.1, Windows Defender antivirus is already installed. It's not rated the highest in the bunch, but I like it. I use it along with Malwarebytes Pro and have had very good luck with it.
Avast is probably rated the highest of the free options, but I got rid of it because I got tired of having to renew my subscription every year so they could bombard me with requests to upgrade to the paid version. I got rid of AVG because it hogged so many resources - my hard drive was running constantly. I thought they had gotten better, but someone else here at GB said they didn't think so.
You might do a search for the best free antivirus solutions... there might be some recent comparisons.
And how are you liking your snazzy new gaming laptop?!
In my PC corner for the winter, gaming, knitting and reading.