Reformatting disk with no partition map I have a 250GB hard drive that I tried to "burn" an ISO to (to make it bootable). Something went terribly wrong.This is what the disk looks like in Disk Utility (unmounted).



When I mount it, this happens.



I have tried formatting, erasing, verifying, and repairing the disk through Disk Utility and terminal's diskutil command, all to no avail. I have tried deleting the files contained on this hard drive (Windows boot folders/executables) using both the GUI and a sudo command in terminal with no luck. This is a partial output of diskutil list:



The drive is /dev/disk4.

I consider myself decently knowledgable in technology in general, but this problem has been very difficult. Can someone please help me? Please feel free to leave any questions or comments below.
Remove all external disks (just for safety reasons). If possible also remove all internal disks except the boot disk or "refresh" your backups.

The proposed command (dd) used improperly can be deadly for your data.

Open Terminal.app and get the disk identifier of the disk containing the DVD partition:

diskutil list


Unmount the disk:

#replace diskX by the disk identifier of the "DVD disk" you found previously
diskutil umountDisk /dev/diskX


Overwrite the first sectors of the disk with

sudo dd if=/dev/zero of=/dev/diskX bs=4096 count=8


This will zero the first 8 physical blocks (or 8 4k/64 512b logical blocks) of the partition and should remove any "DVD hints".

Open Disk Utility and try to erase/repartition the disk again.