When creating a Virtual Client, you must select the plugin the Virtual Client will use. By default only the file system plugin for the operating system of the NetVault Backup server will be available in the dropdown.
For Oralce, SQL and Exchange plugins, download the plugin which will be needed and place it somewhere under the packages folder. (e.g. C:\Program Files (x86)\Quest Software\NetVault Backup\packages\extra)
If you are creating a Virtual Client that will use the File System plugin for a different OS than the NetVault Backup server, copy the correct .npk plugin file from the NetVault Backup client to the NetVault Backup server.