All one really needs to know about virus is that they are transmitted through attachments....so, never open an attachment that you aren't expecting, even if from a friend. Twice I have received unexpected emails with attachments, from people I regularly correspond with...but, as I wasn't planning on getting anything from them, before opening, I dropped them an email, asking if they had sent me something,. In both cases, they hadn't, but were unknowingly infected themselves, and equally unknowingly busily infecting others. These things work, at least the ones I've dealt with, by an infected computer sending emails to everyone in it's address book, and when these attachments are opened, they infect the computer receiving it. Thus, if you never open an attachment without knowing what's in it, you'll never get a virus (at least until something "new" comes along.")