Mytob and Zytob Virus
We have seen a large number of Mytob and Zytob virus infected e-mails.
This particular family of virus's has been around for a while but their primary characteristic is a zip file attachment.
These messages have several different characteristics besides the zip file attachment but most appear to be messages from your Internet service provider telling you that your account has some type of a problem and to open the attachment for more information. Once the infected attachment is opened then your computer is infected and sending out the same type of infected e-mail to all of your friends.

For a detailed description and a removal tool see Symantec's Mytob Worm page.
Also for a detailed description and a removal tool see Symantec's Zytob Worm page.
As always be careful when opening suspicious e-mail attachements, install and run up to date virus protection, and keep your Windows up to date to protect your computer from virus's.