Image files made with Disk Utility creates parent folder
I'm pretty sure you created the image wrong. When you create the image in Disk Utility, it's very important that you specify the source correctly. I'm not certain I remember exactly right, so you should test this before you trust the results, but here's the process as I remember it:

In Disk Utility's sidebar, select the DVD's entry. IIRC, it'll actually list two entries in the sidebar: the DVD itself, and then indented under that the installer volume (&quot;Mac OS X Install DVD&quot; or something like that. You want the DVD entry, not the volume entry under it.
IIRC older versions of Disk Utility would actually list three entries: the DVD, a session under that, and the volume under that. In this case, I'm pretty sure it's the session (the middle entry) you want.

Under the File menu, choose &quot;New&quot; &gt; &quot;Image from disk2&quot; (or whatever the disk ID is). This tells Disk Utility you want a raw device image, not just image the files contained in the disk.

In the save dialog, set the Image Format to &quot;DVD/CD master&quot;


I think that procedure will work, but to be sure it's best to rename the file from &quot;.cdr&quot; to &quot;.iso&quot;, copy it to your Windows computer, burn it to a DVD-R, and actually try booting the Mac from it. Note that if you mount the .iso on Windows you will not see anything like what you expect -- IIRC the 10.5 install DVDs are actually in a hybrid format that contains a Windows-readable driver disk for Boot Camp, and a Mac-readable (&amp; bootable) installer volume. So if you mount it on Windows, you'll see Windows drivers, not a Mac installer. (BTW, this is also true of the original DVD, so try mounting that on your Windows computer to check my memory.)