[http://www.ntpro.nl/blog/uploads/plugin.JPG]

Plugins extend the capabilities of VirtualCenter by adding features and functionality not present in the base product. Generally, plugins have a server component and a client component. After the server component of a plugin is registered with a VirtualCenter server, the client component is available to all VirtualCenter clients connected to that VirtualCenter server. Users can download the client component of the plugin through the VirtualCenter client plugin manager. Users can select to enable or disable plugins installed in their VirtualCenter client. Disabling a plugin does not uninstall it from the client; it merely disables the functionality of the plugin. The VirtualCenter client interface might change after a plugin is enabled. New views, tabs, menus, and menu options related to the plugin's features are added to the interface. Existing interface items are not affected. The base product and plugins can be upgraded independent of each other. To reach the plugin manager, select Plugins > Manage Plugins.

http://www.ntpro.nl/blog/archives/228-ESX-3i-Manage-Plugins.html

On the carton box where the key was shiped in there is a warning about adding the server to an existing VC server.