Poser 5 had an activation requirement that was removed with SR4, Poser 6-10 only require the Serial Number. The biggest problem you are going to run into is the Service Releases are no longer available for any of the Prior Versions of Poser.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13