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I had an unmountable floppy image (.img) that contained an operating system I had made and I used disk utility to burn it to a CD. It said that the burn was successful.

I tried to boot it from VirtualBox, which had worked with the image, but it wasn't successful. I tried to erase the disk but Disk Utility wouldn't let me. It also wouldn't let me burn a different image to the disk or use first aid. How can I erase the disk so it is usable again?

I am using a MacBook.

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up vote 1 down vote accepted

If the CD is not re-writable, no software in the world will be able to write over it (successfully). If your CD is a CD-RW, then you should be able to erase it just like any other disc.

With respect to the rest of the problem, I'd like to suggest that it's probably not best to try to burn an *.img file to a CD. Typically, CDs can be burned from *.iso images, but *.img files are usually designed for floppy disks or flash drives. If you're just trying to boot Virtualbox from an *.img file, I recommend converting it to a *.vdi via the following command:

VBoxManage convertfromraw -format VDI [filename].img [filename].vdi

Then just add the *.vdi to your virtual machine as a virtual hard drive.

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Many .img files are simply ISO images with a .img extension. And if a CD/DVD burner recognizes the file format, there's no reason why it can't be successfully burned to an optical disk. There's nothing magical about floppies or optical storage that prevents data from being transferred from one to the other. His problem was likely due to an error during the burning process or faulty media. – Lèse majesté Mar 11 '12 at 21:58

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