Thanks for asking Michael. Here are the softwares I use:
1. Backup: SynchBack
http://www.2brightsparks.com/freeware/freeware-hub.html
I have a 250GB hard-drive for backup.
2. Anti-virus: Clamwin
http://www.clamwin.com/
I don't use a Firewall. With my ISP, a firewall leads to more problems than its worth it. But if I had to use one, I would use Comodo.
http://www.personalfirewall.comodo.com/
All of these softwares are free.
I do run Ad-aware once a month too.
http://www.lavasoftusa.com/products/ad_aware_free.php