I've tried twice to write a debian ISO to a cd-r but there are write errors. Are the disks ruined?

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http://unix.stackexchange.com – I know that in Windows I was able to format blank cd-r to work as USB so I'm wondering if I can still do that even though they have corrupted iso images burned onto them. (Right now I'm in Ubuntu) I'm using k3b to burn the images and both times I tried, the installation wouldn't complete because of problems with the disk. So now I have two useless debian installation disks lying around and I don't know how many more tries this is going to take. I'd like to be able to do at least something with them so I'm not just stacking up ruined cd-rs one after the other. (HowTos)