I realize I'm way late to an old thread, but this might be helpful to someone who comes along and reads it.

The difference between registered and non-registered is in the type and amount of damages you can receive. For infringement of non-registered material, you can only collect for actual value, while for registered material you can collect punitive damages and court court costs etc.

The time limit folks are referencing has nothing to do with the date of creation of the work, but rather the date of PUBLICATION.

Carolyn Wright is a photographer and attorney who deals with copyright issues frequently on her blog as well as on another photography forum out there on the WWW.

Her blog is here: http://www.photoattorney.com/