antivirus in windows

Do you mean norton power eraser or a paid norton product as on demand scanner?
 
As possible UAC + SmartScreen + Windows Defender should be enough for you, its protection capabilities can prevent known common threats but if you want to browse on some dark side of Web then suggest to add Sandboxie.

For browser you may add Opera as its one to be reliable browser, extensions for optimization is Adguard and HTTPS Everywhere.

Optional suggestion: Lastpass for storing sensitive informations and password in secure way.
 
Some type of backup
CCleaner or Privazer
Some on demand scanners. norton??
No need to double post with a personal verification