All-In-One

Windows Live Safety Center

Anti-Spyware

Windows Defender (Beta2)
SuperAntiSpyware
Ad-AwareSE
Spybot S&D
Hijackthis

Anti-Virus

CLAMWIN
AVG
Avast

F-Prot

Registry Cleaner

Easy Cleaner

Personal Firewall

Comodo

Miscellaneous

JkDefrag - Free defrag utility
CCleaner
Sysinternals
Autoruns
MS BootVis