Memory Card Not Formatted Nokia

"I cannot access the memory card which has used for my Nokia mobile phone for about two years. The card still worked normally yesterday, but today it says that the memory card needs to be formatted. All files stored on this memory card become inaccessible. Nokia mobile phone always reports the same error message that memory card needs to be formatted. Connecting the card to another mobile phone, I still get the same error message. Then, I inserted the card to my laptop, and Windows system still said that memory card is not formatted. How can I fix thenot formatted error on Nokia memory card? Is it possible to get back those inaccessible files?"