I have to agree that sending them trojans was not a good idea. Aside from the spreading of malware, people have been killed that have been victims of 419 scams.... It's not a good idea to play with these people.
The proper thing to do is to report them on
www.nipc.gov That is the FBI's syber crime website, now split into two sites
www.us-cert.gov They have fraud report forms for you to fill out, they are not long and only take a second to fill out. You capture the headers of the e-mail and paste them into the form as well.
That is the proper step to take. After filling out the form, you delete the message and don't look back.
I don't care if you're a Navy Seal or an Army Ranger, playing with those scammers is a very very bad thing to do. Many of them have ties with Organized crime of various countries.
Report them and forget them should be the thing to remember when getting a 419 scam e-mail, especially if you're selling something and they've sent you an e-mail about it. Much more personal than a random Neigerian 419 spammed e-mail....
At the very least delete the e-mail and forget about it....
take heed of what I say, or don't, it's your choice,
Mike B