Phew, calm down buddy, no need to get all fired up because of one idiotic retard.
If you try to get help from sites that do this kinda stuff, you could help there, or, you use the program R.A.T and try to DDO attack him, either way, goodluck.
Quick edit:
Bomb his MSN, try to send out trojans and harass him, that's what I would've, but mate, I understand you, getting ripped off sucks