What format is the original DVD in -- HFS+? UDF?
What kind of disk image did you make with Disk Utility? .cdr? .img?
The proper way would have been to burn the original DVD in UDF format, then make a .cdr image using Disk Utility, then use Disk Utility to burn copies.
If your original DVD is in HFS+ format, then the disk image you create and the subsequent copies made will also be HFS+, meaning they cannot be read on a Windows machine without some commercial (non-free) software that reads the HFS+ format.
Does the original DVD read in a Windows machine?