My samsung NV100HD camera is telling me the card is locked how do i unlock it???

You can probably tell that this is a 'standard answer' that I wrote a little while ago, but to be honest with you, it's a 'standard question' that gets asked a lot! I'm pretty sure Samsung cameras like your NV100HD use SD cards, so it applies to you:

Why does my camera say "Card Locked" or "Write Protected"?

The basics. In the same way that the recordings on audio cassettes and VHS tapes could be protected by breaking off the little tab on the back corner, the material on a memory card can be protected against being overwritten. Instead of a tab to break off, write protection is done by a tiny slider on the edge of the card (opposite the cut corner). Before the camera will take pictures, it's necessary that this slider on the card operates a microswitch in the camera, which it will only do if it's NOT in the 'lock' position. The slider actually does nothing inside the card, which is why I don't call it a 'switch' even though it seems like one. Its only purpose is to be detected by the microswitch in the camera's slot, and it's the camera that takes care of the write protection, not the card.

Diagnosis. Obviously the first thing to do is to check that the slider is NOT in the lock position. If the camera is giving you this error in the unlock position, it means that the slider has failed to operate the microswitch, or that the microswitch itself is faulty, or possibly that there's some file system error with the card. To diganose the problem, it would be really helpful if you could try two or more different memory cards in the camera and see if just one, or all of them exhibit the problem.

If only one memory card exhibits the problem: In this case, it's clearly something to do with the memory card. Is the slider worn, bent or missing? A missing slider will write protect the card in the same way that sliding it to the 'lock' position will. There's another possibility. I've recently discovered that some cameras which use xD-Picture cards also give this error even though those cards don't even have lock sliders! Furthermore, some users have reported fixing this error by reformatting the card. Therefore, I feel it's also possible that your error may be fixed by reformatting. Before you do this, make sure that you've copied all you want off the card and then use the camera's 'format' function to reformat the card. I advise using the camera for the format function because this guarantees the correct file system. If you use your computer to format it, you may easily get the wrong one. However if you need to do it this way, see which file system is currently in use on the drive before you start. Go to "My Computer" and right click on the drive which is the memory card, and choose "Properties". Examples of filesystems are "FAT" (probably FAT16), "FAT32" and NTFS; to make sure your reformat is successful, ensure you use the same filesystem as before.

If some memory cards work, and others don't, or the same cards sometimes work but only sometimes: The slider is really tiny, so it's possible that the number of people reporting this error is caused by lack of precision in manufacturing sizes. It must be hard to make a microswitch that can feel such a small thing. Does a better brand of card work? Can you bear to simply stick to the better brands, or the ones that work most reliably? As a remedy of last resort, you could try wrapping a small strip of sticky tape over the slider to increase its thickness, but I think this is a risky solution. There's a risk that the tape will come off in the slot and cause even more problems, or that the tape will be so thick that the card will jam in the slot and you'll have trouble getting it out.

If all of your memory cards behave in the same way: In this case, it's clearly something to do with the camera. It could be that the microswitch is broken, or there's some software error. Although it's less likely, let's cover the software error first; please find the 'system reset' function in your settings menu and use it to clear everything. Any good? If not, try the sticky tape solution in the last paragraph in the hope that it's a size/fit problem with operating the microswitch, but if that fails we're out of options really, beyond a repair of that microswitch.