Which is the best antivirus? HELP!!?

I have the following antivirus setup with me

1. AVG75free_519a1276 (AVG 7.5) = 34.2 MB size

2. bitdefender_antivirus_2008_32b (bitdefender antivirus 2008) = 34.1 MB size

3. kav7.0.1.325en (kapersky 7.1) = 29.6 MB size

Which of these are trial versions ? Is the bitdefender full version ? Which among these 3 is the best ?

When i try to instal bitdefender, it checks for new version and asks me whether to download the new version .. I heard bitdefender is the best in 2008 survey, is it true ?

AM using Windows vista, so have already a windows firewall, i just need a basic virus scanner that can find virus in pen drives and other removable media.

Which is the best antivirus? HELP!!?adware remover

4.Avast Home Edition

http://avast.com/eng/avast_4_home.html

Which is the best antivirus? HELP!!?antivirus protection

For the record..... you see the top antivirus prize the VB100Award. Symantec Norton (USA) has been number one for years until a few ago when Kaspersky (Russia) now enjoys those honors UNTIL now - Trend Micro has taken the title over them and NOD32 and AVG and all the rest.

Trend Micro(TM) Internet Security(TM) 2008 Achieves Top Scores in Anti-Malware Testing

Trend Micro(TM) Internet Security(TM) 2008 Achieves Top Scores in Anti-Malware Testing (PR Newswire via Yahoo! Finance)