Have a look in Help > About Installed Plugins, and that will tell you if it installed properly. It is called ‘Genesis Generation X’, and is near the bottom of the list.
I did get the update.
Do you mean that you bought the Upgrade version? That is for former purchasers of the ‘Gen 4’ plugin from Renderosity, and you will need your Order Number from there to activate it I believe. My plugin says it is version 1.2, and I am on DS 4.5, Win 7 as well.