Boot Option Missing! Please Help!!

Dear Apple Community

I am a new macbook pro user, I installed windows 7 32 bits edition via bootcamp, it has always been working fine. Earlier today the windows crashed and when the system restarts I cannot find windows 7 boot option at startup while holding the Option key down. I tried to Command Option P R, Command R, nothing fixed it. I can still see my windows files when I open my finder in Mac OS. Is there a way to restore my windows on startup? I really needed it.

Thank you!

Laura