free home antivirus

I’m using prgm version 2015.10.0.2218 on Vista, and I can’t get the file shield to turn on. I tried clicking on fix now and by going in to turn it on myself. >:(
Also, it says new program version is available, but there’s no new updates for the program or virus definitions. :o
How do I fix these issues? :-\

Thanks! 8)

Z

Repair Avast:

  1. Control Panel → Add/Remove programs → Avast
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.