Download Free Software Antivirus

Hey guys you can download below antiviruses for free,These are top antiviruses for 2008.
avast! 4 Home Edition
AVG Anti-Virus Free Edition
Avira AntiVir Personal Edition Classic
HijackThis
NanoScan
ThreatFire AntiVirus
Trend Micro HouseCall

I have been using HijackThis but i am looking forward to use avast! 4 Home Edition, just wanted to know if you have used it. Iy would be very helpful if you will share your experience with avast! 4 Home Edition including its negative and positive aspect.