Solution for above error message is to remove or Disconnect “Floppy” from your Windows Virtual Machine. (Actually autoinst.flp. file contains the ProductKey & autoinst.flp is mounted when you start the VM)Power off Windows 8 Virtual Machine & Go to Virtual Machine settings & remove the Floppy. Now you can installWindows 8 without any issues. Enjoy!!
Also check How install Windows 8 customer preview on VMware Workstation & Virtual Box guide,