if you are using outlook express right click on the message then click on details... then look at the recieved from then get the ip... then go to http://www.geobytes.com/IpLocator.htm
also this will show where the isp is located not his house... so you will prolly have to go to a couple of peoples houses and get on there computer and go to www.whatismyip.com
and then see if it matches up...
or you can tracert it to do this go to start then run then type CMD then type
(replace the x's with the ip)
look toward the bottom and you can see what there ISP is it should list a server name and like it may say sprint or earthlink or one of those... and then if you know the friend who has that ISP then you will know who it is...
here is a picture about where the ip is...
***NOTE TO MODS***
yes that is the ip for CF but anyone can see it so dont get mad at me