點解電腦問我是否將SD card 格式化

It is VERY easy to corrupt an SD card with contents. Try removing an SD card from a camera, plug it into somewhere else (eg. card reader), then plug it back to the camera. Chances are you may corrupt the file system of the SD card.
Seems that your SD card's file system has been corrupted. You will need data rescue software to retrieve all contents from the card.
It is not highly recommended to use consumer-grade image rescue software since they won't recover original file names, nor multimedia files (eg. movie clips in various formats).
Industrial grade data recovery software may pull off the job nicely, but it's beyond ordinary people's reach.
More info regarding such software will be sent to you via PM.

2008-02-25 04:17:15 補充：
If you have a corrupted card you need NOT format it prior to data rescue. Just plug in the card and run the data rescue software.Otherwise, if you format the card the WRONG way (low-level format for example), you will NOT be able to recover ANY data.

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