Bagles and Alphabet Soup
Several variants of the Bagle Virus (bagle.r, bagle.s, bagle.t) have surfaced in the last couple of weeks. These infect computers without having to open the attachment. They apparently exploit a hole in Windows that was fixed by a patch a while ago. You should always make sure you have done your Windows Updates regularly. You can do this by clicking on Start then All Programs then Windows Update and then following the prompts. If you haven't done this in a while, it could take quite some time to complete them, but it is well worth it.
If you are getting returned mail stating that a virus came from your computer,
it is the result of the new Novarg/Mydoom virus circulating on the Internet.
The messages originate from other Internet users who have been infected and has your email address in their contact list. The virus sends out emails from the infected computer and picks a random email to be placed in the "From" field making it appear to be coming from someone other than from the person with the infected computer. If the virus attempts to send out email to an invalid email address which a mail server does not accept and, if your email address is used in the "From" field, the message bounces back to you.