|If the ISO you have is supposed to be a bootable image, then you burned the disk incorrectly.|
The above answer is correct as far as it goes--when you use your burner software to "make a bootable disk" it will probably use the DR DOS boot image by default, but---
if the ENTIRE IMAGE (ISO) is already supposed to be a "bootable image" then you are using the wrong procedure. When you "burn" an ISO to a disk, you don't copy the ISO to the disk, rather the ISO, together with the burner software, "manufactures" the entire disk, and when you get done, it will have the coorrect boot image.
Since I'm not familiar with whatever your software "is" I can't lead you through that.