There's a number of ways.
The best way is to look at the email header. There's a good article on about.com at
http://compnetworking.about.com/od/w...dressemail.htm (skip to the next part of this post before doing all of that, though). That basically deals with finding headers which contain IP addresses. Another great article at
http://www.stopspam.org/email/headers.html as well.
Essentially, what you'll have to do is right click on the message while it's in your inbox (or wherever you saved the message), click on "properties" (sometimes it will be "options" depending on your email client...I use Outlook Express and it's listed as properties), then click on the "details" tab and then copy and paste what you see. From that, you can get the IP address of the sender and, with a little trickery, get their ISP. Booyah.
I take it you bought this stuff through vtechonda.com? That's where the 2nd number comes back, anyway. Amazingly, the 1st number leades to the address you listed (of Mark Fontaine), although that doesn't mean a whole lot.