To your first question I reckon you read here:
http://www.gnutellaforums.com/showth...176#post154176

Your second question:
Spybot - Search & Destroy (FREE)"]Spybot - Search & Destroy (FREE)[/URL]

http://www.lavasoftusa.com/software/adaware/(free)

AVG free Anti virus program

Anti malware (trial version that still can be used after the trial period)


To your last question:
Yes, you should scan all files you've downloaded individually

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"Never Argue With An Idiot. They Will Drag You Down To Their Level, Then Beat You With Experience"