Heh... that scam is really common right now. I had an idiot send me an obviously fake $4000 cashiers check for a $150 keyboard. I knew it was a scam from the second email he sent me.

Know what I did? I kept all those emails, put them in a word file and printed them out. Then I took those, the envelope the check came in (with a different name on it) and the check (with TWO different names on it) to the bank and handed it all over. They made copies for me and sent the rest to the cops. BUSTED!
I was even able to do it a second time, tho only with emails, when another idiot tried the same thing only 4 days later!

So be aware, folks, some of those scammers are good... but with an alert eye you can get the better of them.