You'll need to run a 'checkdisk' which you can do by right-clicking the 'C' drive and hitting properties then tools. Make sure after you've hit the 'check now' button you check the little box for 'attempting to repair and recover bad sectors', then reboot..
If the disk has become so damaged that you can't get it to run then you'll need to go 'proffessional' to get the information you want. If you google for data reclamation firms and the like you should find someone that can help

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