There are no drive designations in Linux. Everything is under the root file system, which is / - user directories are under /home, user commands are in /usr/bin, etc. As a simple user, usually you will be working in your /home/userid directory.
As for free anti-virus for Linux, the most commonly used one is ClamAV. You can get that at www.clamav.net
rubberman
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Also, most systems have ClamAV in their repositories so you should only need to execute "yum install clamav" as root from a command-line.
rubberman
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Linux AV is useful if you are using your system as a mail, web, or file sharing host, in order to scan files and emails as they are uploaded and stored to the system. Clam is popular for that.
rubberman
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