What country are you talking about, here? If it’s the US, then all authors have copyright of their works when they create them, by default. You don’t even have to put the little © symbol. If you really want to bring an infringement lawsuit against someone, though, you’ll be a lot better off if your work has been registered with the US Copyright office. If not, you’d better have some kind of real proof (i.e. public display, strong-crypto signed and date stamped), previous to the infringers display of the work or you’ll probably have a tough time getting anything done.
And, contrary to urban legend, mailing the work to yourself and claiming the US Post Office postmark as proof of date doesn’t cut it.
If you have either registered your work, or can clearly demonstrate your prior ownership of the work, then go get yourself a copyright attorney and sue. Regardless of what the RIAA or MPAA would try to get folks to believe, copyright violation is not a major criminal offense. You’ll be taking them to civil court.
Why the ?'s? Is someone violating the copyrights on your work?