After i select the BT4 iso, i got the message:
Failed to open the CD/DVD image /home/owner/Documents/bt4-r2.iso.
Could not get the storage format of the medium '/home/owner/Documents/bt4-r2.iso' (VERR_NOT_SUPPORTED).
Details:
Result Code:
VBOX_E_IPRT_ERROR (0x80BB0005)
Component:
Medium
Interface:
IMedium {9edda847-1279-4b0a-9af7-9d66251ccc18}
Callee:
IVirtualBox {d2de270c-1d4b-4c9e-843f-bbb9b47269ff}

This has been bugging me for a while. I haven't found any idea that helps anywhere so does anyone have any ideas?

Thanks in advance.