After looked into VirtualBox forum, I found the actual cause to this problem. A few days ago I converted the same VDI virtual disk into RAW format using vboxmanage command and I deleted the virtual disk today without properly releasing it from Virtualbox media manager. So the Virtualbox box still thinks that there is an already registered virtual disk exits with the same UUID and refused to create a new one. To fix this, I should release and then remove the registered medium.
We can release and remove medium (hard disk or cdrom) in two ways:
- Using voxmanage command,
- Using Virtual media manager.
