Recently a friend asked me for recommendations for free antivirus and anti-spyware programs for a old PC he is retrofitting for his parents. Thought I will share these links to others as well.

Antivirus:
AVG
Avira
Avast

Firewall:
Comodo
Online Armor
Zonealarm

Antispyware (haven't really found any great ones yet)
Spybot
Ad-aware
Microsoft Windows Defender(provided your version of windows is authenticated)

Others stuff you should install :
Firefox
Peerguardian 2 ;p

Any other recommendations are welcome.