Please every body Help Me My Drive D lost

I'm use window7 operating system x64.
Thus the incedences.
Im install the program, on midle installation appear blue screen and im read this blue screen is dumping, after that my pc restart by itself.
And i'm open explorer, arrived my Drive D lost and drive C only remaining wich can been accessed.
Please tell me how to solved this problem.
I'm very dizzy because data on that drive D, very important for my work and my life .

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