My humble opinion on Virus:

If you download files any where from the Internet especially from a file sharing program it is ESENTIAL to have a Virus program and to keep the virus signatures up to date. Also a Firewall program is equally ESENTIAL.

I use ZoneAlarm a free firewall program which works superb for me. It can be obtained at "http://www.zonelabs.com/index.html"

I use InoculateIT an excellent virus program which is no longer free but works well and does not interfere with other programs as readily as McAufee. It can be set to virus scan downloads automatically. It caught a Virus file for me and cleaned it and deleted it. In any event it is a MUST to also Virus Scan any file after you download and before you open it.
InoculateIT can be obtained at: "http://antivirus.cai.com/"

Anyone who does not use a Virus and Firewall program and downloads files is at GREAT RISK.