Memory Stick Needs Formatting Message

"I have a 2GB memory stick for my Sony digital camera, but the problem is that I cannot access the memory stick. When I inserted it to my PC, it says disk in drive is not formatted do you want to format it now? I also receive CHKDSK RAW error on memory stick. Reinserting it to my digital camera, it also said that memory stick needs to be formatted before I can use it. I cannot format the memory stick because it contains lots of important data without any backup. Please tell me how to recover data when a memory stick asks to be formatted in both digital camera and computer? How to fix the not formatted error without formatting?"