Problems with CDs burned with hdiutil

[dcg]

Over the weekend hard drive got scrambled, Finder wouldn't start, fsck didn't work, nor did Disk Utilities, so I was going to have to reformat the HD. Needed to backup items before doing so, saw that you could use hdiutil to create an image file from a folder and then burn that image to CD. Did that


du -s myFolder which would give me the sector size X of myFolder
hdiutil create -sectors X myFolder where Y was bigger than X by about 1000-10000
hdiutil burn myFolder.dmg

It then prompted me to enter the CD, which was burned and verified. I did this about 7 times for all of the folders that I needed backed up, replacing 'myFolder' with the obviously folder of interest.

Having reformatted and reinstalled OS X, I put the CD into the drive bay to copy the files back onto the HD, only OS X told me (and yes, it talks to me) that 'You have inserted a disk containing no volumes that Mac OS X can read. To continue with the disk inserted, click Ignore'.

I presume that I did something wrong in creating the DMG files and burning them. What would that have been? Secondly, is there any way to get the DMG files from these otherwise unreadable CDs? Thanks a lot.