This is the most tried to be used scam on our sister site http://www.freefluteclassifieds.com. We can't get rid of people trying to do this. All sites that do auctions or classifieds have the same problem.
 
Keep in mind (on FreeFluteClassifieds.com at least) they never know your email address. They just are using the "Reply to Ad" button. The server sends you this kind of a email. Just don't communicate with them in any way. Just ignore that email from the server. They will go away. We will report them to SpamHaus.org. And remember, they still DO NOT know your email address if you do not email them back.]  
 
 
-The 'Nigerian' Purchase Scam-
You receive an email from someone wanting to buy somthing from you/your website, he wants to pay by check and (usually) wants you to ship the products to his address in Lagos, Nigeria.
 
The variants on this scam often involve:
A payment via check is made, but (some weeks later) is returned by the bank on which it's drawn because it was forged. The scammer counts on your willingness to ship the product after your bank has (provisionally) cleared the check, and before the check has cleared its way through the whole international banking system.
 
An "accidental" overpayment by the buyer, who asks you to deposit the check and then refund the amount of the "overpayment" when you ship the goods. You're out both the cost of the goods, and whatever "overpayment" you refund, when you find that the original check is made of rubber.
 
-from SpamHaus.org-

Wow this happened to me when I was trying to sell one of my flutes.