Guest operating system ‘fedora’ is not supported.Please select a guest operating system from the General page on the Options tab of Virtual Machine Settings.
大致意思为Fedora不能被支持，请在设置 里的General page选项标签选择合适的操作系统。
google之，原来在Setting菜单 Options标签的General选项里公然把Fedora识别成了Ubuntu，改为Linux 2.6后再启动虚拟机时，OK了。