The standalone (non bundled JRE) Installer will need a JRE to start with and to set for CERTivity. If you are using the standalone Installer make sure your system has a Sun Microsystems (Oracle) JRE available for the user you intend to use to install CERTivity. If not, then please install JRE 1.6 or higher according to the Java vendors instructions.
The standalone Installer will automatically look for a suitable JRE on your platform for the installation itself and for configuring CERTivity to start with. The minimum required version is 1.6.