How do I copy to DVD my VirtualBox Windows data?

I urgently need to make a backup before my hard-disk crashes. I realize this is an unusual request but I actually would be unhappy if my disk crashed.

How can I burn a "data files" type of DVD from the Windows virtual drive inside of VirtualBox?

CDBurnerXP cannot see the DVD drive offered by VirtualBox. In detail, within CDBurnerXP the drop down box for the destination device does not list the DVD drive even though the VirtualBox Device menu has the DVD drive "checked" or selected for passing through to Windows, although this might to be the same as the Passthrough setting in Machine, Settings, Storage. The error given by CDBurnerXP is "no burner selected" and the drop down lists "no compatible drives" and there are no alternatives given. (Aside: I used CDBurnerXP because Windows 7 is incapable of deep tree disk burning because backups are an unusual an unimportant matter. I am on Windows 8 but I am presuming that it continues to have the same problem.)

Using Windows File Explorer which used to be called Windows Explorer there does not seem to be a DVD burning operation on offer.

Opening D drive, which is a blank DVD, fails since it's not a Windows file system, so there seems to be no way to drag a file into it (nor copy-and-paste) as a means of burning the disk.

Is there a way to use Ubuntu to burn the Windows virtual disk as "data files"? I realize I could probably burn it as one big ext4 file but then I don't know if I would be able to do a restore that would be compatible with the state of the virtual machine. Furthermore, I would guess that a partial restore of selected Windows data is out of the question. If I burn a big ext4 file that is the entire Windows virtual machine folder, would that be compatible with meta-data elsewhere in the ubuntu file system?

Edit: Without anyway to backup individual Windows files, I presume it is harmless to backup the whole virtual machine folder, nuke it, then restore the ext4 file into ubuntu but I would have to make an alternative backup before I would risk testing this. I will update if I have practical test results.

Seems that your virtual guest not detecting your host CD drive. So, first make sure you have installed guest addition. Then choose your host drive going to Settings --> Storage and then choose your host cd driver:

Or You can mount ubuntu on windows and move all windows file to Ubuntu and then burn or something. check this answer Auto-mount shared folders using Virtualbox Manager

The fastest, safest, and only recommended way to backup your Virtual Machine is mounting an external drive on your host system to then export the Virtual Machine from Virtual Box Manager File -> Export Appliance.

Select one or several virtual machines to export.

Choose the mount point of your external storage device.

Only exported virtual appliances can easily be re-imported with all their settings to a new instance of Virtual Box.

The size of the exported machine will be considerably smaller than the virtual hard drive size if you had chosen a dynamically growing drive.

It is not recommended to store the backup on your dying hard drive, as this will put all of your data at further risk.

To access to your host DVD/CD-ROM drive for write access you will have to enable passthrough in the storage menu as shown in the answer above.