If you on Windows Visa or 7 and have Poser installed with standard options, the installer won't be able to put V3 in the main library. Make a new runtime directorys outside of the areas protected by Windows. Run the installer for "DAZ Studio" if it does not work otherwhise. But don't use posers main runtime for downloaded stuff. 

A ship in port is safe; but that is not what ships are built for.
Sail out to sea and do new things.
-"Amazing Grace" Hopper

Avatar image of me done by Chidori.