Hello, I suggest you to install PrivaZer for privacy, then you can install BitDefender 60 second virus scanner, because it's a quick and light scanner and it runs in background.
So, you can install also Collusion extension for your browser, which allows you to know which websites are tracking you, and this is very important.
Then you can also install Auslogics Disk Defrag, which can improve the speed of the PC and in addition also MPC-HC, which is a very good and fast media-player.
Thanks for sharing it