Most virus emails are generated by mail servers the offender has at their house. This will always leave an trace (their external IP). I urge everyone to use this IP address and do a back trace.

You can do a domain reverse ip search here, http://www2.cqcounter.com/whois/. This should give you the name and website of the ISP. Most ISPs in modern countries will have abuse emails or links to abuse forms.

If you use Outlook or Outlook express, you can save your email as a .msg document to your desktop. THen open it using Notepad, the IP address will look something like, X-ClientAddr: XX.XXX.XXX.XXX