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When accessing an SD-HC card on Snow Leapard many of the options to erase, partition and repair are disabled. The disk is appearing as a read-only file system formatted in FAT-32 so I can't delete the files on it. How do I erase data on the disk?

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up vote 1 down vote accepted

You unlock the write protection of the SD card.

On the left side may be a write-protection notch. If this is present, the card cannot be written. If the notch is covered by a sliding write protection tab, or absent, then the card is writeable. Because the notch is detected only by the reader, the protection can be overridden if desired (and if supported by the reader). Not all devices support write protection, which is an optional feature of the SD standard.

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Doh! What a donkey. Forgot about that tab. Thanks. – Stephen Oct 31 '10 at 15:40

I had the same problem. It wasnt the slider lock though. I finally figured out that the SD card reader was plugged into a USB hub which for some bizarre reason only could read and not write files nor erase/format the SD card. I plugged the reader straight into the back of my Mac and hey presto..the card formats and I can now write files to it!!! (if anyone can tell me why read-only happens through the USB hub I'd be very curious to find out).

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Could be a disconnected pin or part of the cable – Canadian Luke Apr 3 '12 at 6:38

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