Lich

take your DVD to a video game store or something and have them buff out the scratches and sand down the disc, that should help. Then if the DVD is older, DVD shrink should be able to handle it no problem. If not, try DVD Decryptor, which I've had good success with. You'll need to run the large ISO throuhDVD shrink when you're done copying it, but then you'll have a good, working backup.

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lectricpharaoh

Nono, that's not what I meant. Imagine sector X is bad. If you read it, it gives a certain result. But, because it's bad, if you read it again, you're likely to get a different result. Read this sector several times, and if you get the same result each time, it's a properly-formatted sector (and thus exists on a copied disk). Using low-level I/O won't get around it. Low-level I/O might help with the other stunts they used to make the disk difficult to copy (such as different tracks having varying numbers of sectors), but it won't help with the bad sector trick.

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nnxion

Thank you for the insight. How about creating your own diskreader which is able to scratch the disk with its header, so instead of formatting it writes bad sectors. (I'm not sure if that's even possible.)

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lectricpharaoh

Dunno about that. When I say 'bad sectors', I don't mean physically damaged (though they might be). I just mean ones that are not formatted. Those little magnetic domains that indicate ones and zeroes are not aligned in a manner so as to clearly and consistently read as one or the other. Since many floppies come 'preformatted', and have for years, it would seem to be difficult to acquire a truly unformatted one. It might be possible to ruin it with a magnet, degauss it, or something, and then do a low-level format/copy operation to affect only those areas of the disk which were to be 'good sectors', but I'm not certain. I expect that the companies that used techniques like this had hardware that's not available to your average computer nerd.

Nowadays, it's a non-issue, with nobody using floppies for commercial software distribution. They're basically relegated to the role of emergency boot disks and sneakernet file transfer for people too cheap to pick up a USB keydrive, or in situations where such devices aren't supported. Today, copy protection methods tend to revolve around encryption of data, and detecting physical differences between factory (pressed) and copied (burned) optical disks.

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DaWei

The purpose of formatting isn't to organize the randomized domains, which is fairly irrelevant. It's to lay down a framework defining the organization of the disk (sectors, etc.) In the earliest days one could get diskettes which were "hard-formatted", which is to say they had holes around the periphery that were detected by photosensors. In hard drives (magnetic) and CDs the head doesn't contact the medium. Physical scratching is out -- you'd scratch the whole dam' drive. As lectric says, you can do much if you merely go low level; the format and the protocols are merely guidelines for transportability.

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