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The short version: Why can't I burn common ISO files on to regular CDs?

The longer version:

I have a stack of CD-Rs, with discs from two different brands. I also have two ISO files with Ubuntu 10.04 and 08.04.

Since CDs and the ISOs are both, as far as I'm aware, old and well established standards, I would expect this to "just work".

However, with both brands of discs, neither images can be burned to the discs, as CDBurnerXP claims the discs fit only 689.64 MB while the ISO sizes are 699.95/694.42 MB.

If I made the ISOs myself, this could easily be be written off as a mistake on my part, but since we're talking about files that are probably downloaded by the hundredthousands or millions, I'm assuming this should work.

In reponse to the comment, these are my assumptions:

  1. CDs are (nearly) always of the same size, 700mb. (They used to be 650, and there are rare exceptions of 800MB, but neither are common today).
  2. Canonical creates ISOs that aim to reach the broadest possible audience, so they create 700mb ISOs.
  3. The ISO files from assumption 2, should be burnable onto discs in assumption 1.

Yet I find myself with a very small difference between disc size and file size, that I can't explain, mostly because my 700mb discs can't actually fit a 700mb file.

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I'm not sure what you're asking. The ISOs are larger than the disks can take. Why that is is hard to say, as we don't have the ISOs in question. Do you want to resize them to fit? – Ƭᴇcʜιᴇ007 Dec 24 '12 at 17:49
Are you certain the image wasn't intended for a DVD? – Mejwell Dec 24 '12 at 18:04
If you define 74-minute CD-Rs as common, then yes, the ISO files simply won't fit, as the discs can only contain around 650 MB. The Ubuntu ISOs, for example, are made for 80-minute CD-Rs, which should fit 700 MB just fine. – slhck Dec 24 '12 at 18:07
@Mejwell, with a filesize within less a single % of a CD? I find that unlikely. – user50849 Dec 24 '12 at 18:09
Have you run a checksum on the ISOs to make sure they are not corrupted or altered? – Trav Dec 24 '12 at 18:22

It's possible you changed some CDBurnerXP setting somewhere that's causing it to choke on those ISOs. Either check if you can reset all settings back to defaults, or uninstall (make sure config is reset to default while doing so) and reinstall, or try a better (IMO) app like ImgBurn instead.

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