it is called Sircam virus

the latest and greatest in virus technology which executes a visual basic script that grabs random files and documents from the HDD and sends them out through outlook (express).
These files (attachments) are characterized by the double extension (the original file name and the overwritten virus extension) and are infectious by themselves.

If you are using outlook express and have scripting enabled, simply opening the email without clicking on the attachment will execute the virus.