Hah, can we say 15 reasons to rename the file on the xbox? (As in not transferring at all other than to back it up!)
First, you should be able to work around your problem. THere's like several I can think of off the top of my head.
First, I am betting that the cd would work if you tried putting it in then shutting down and then starting after a few seconds.
Second what you're assuming is the reason for the box not working can't be the case. The XBOX is perfectly capable of booting without a valid dashboard file.
Reason I know this:
1) To do a hard drive swap one must start the xbox with a hard drive which does NOT contain any dashboard.
I have done this, you literally boot the xbox using the dvd with a blank hard drive. The data is then copied, so long story short the problem is not the missing dashboard.
Here is what to do. Mess around with booting the disk, check to make sure the chip is connected correctly as since you have no dashboard it's not going to pass certification which will cause the error you mention. Last resort just put a zeroed, partitioned blank disk in and recopy.
Seriously, unless something else happened this really shouldn't be a problem. (oh, and if you still can't figure it out you can always just send my your 'f*cked" xbox, as I would be more than happy to uhm... dispose of it.