ms security essential is enough for me. It does not get in my way. Previously had used Avira but switched when it started nagging with popups. You can also have a secondary scanner without realtime.
Just go to safe websites + update applications should be enough. For the paranoid, you can add windows firewall ( I use TinyWall interface), Noscript, remove flash and unneeded plugins, MS EMET for internet facing applications.
And try to use package managers to install applications like portableapps.
Or just switch to linux which is less likely to be target. If someone good wants to hack your pc, you probably cant do much
Edit - HostMan or browser extension ublockOrigin are nice too