You do not have to uninstall at all unless youve some kind of upgrade only installation which I doubt.

If a win user, your current Poser 4 will be under C:/Program Files/Meta Creations/Poser 4 or C:/Program Files/Curious Labs/Poser 4 if you allowed your installer of P4 to go to its default location and depending upon when you purchased it.

Poser 5 will install to C:/Program Files/Curious Labs/Poser 5 by default, and you can have Poser 4, Poser 5 and Poser 6 subdirs all in your Curious Labs or Meta Creations subdir and they all work fine. You can only have one at a time launched however.

Once youve installed your P5, you can import your P4 runtime so you dont have to reinstall all your content.

hope this helps,

Logan