I was installing win10 virtual machine with VirtualBox in unbuntu16.04. I encountered the above problems, and the solutions on the Internet were all wrong. Similar to the following question.

My solution is to put the IOS files you need to load forward as far as possible when allocating the CD-ROM ports, followed by. DVI.

The problem of personal test can be solved.

fatal:No bootable medium found! System halted

It means

Fatal: not found in boot! Crash

First, the system may be forced to shut down before the installation is completed

The second root operation is to delete system files

Third, improper use habits, should let the system shut down normally rather than directly point x forced shutdown

Reason: the image file system could not be found, and the image file could not be found
in the system

In fact, it’s very simple. Select the corresponding system, and then click settings. Operate according to the figure below, click OK, and then start