error message: Failed to open the extension pack [path details] Details: Extension pack name mismatch between the downloaded file and the XML inside it (xml='Oracle VM VirtualBox Extension Pack' file='VirtualBox') solution: rename the extension pack using underscores (spaces in the error message correspond to underscores in real life), e.g.: Oracle_VM_VirtualBox_Extension_Pack-4.0.8-71778.vbox-extpack Also try using the command line method of installing extension packs: VBoxManage help extpack