No recognizing the Hard Drive or not pluging

Hello,
when i plugin the my Hard Drive in the PC and after restarting when i want to install the new windows but MS Dos is not show or no Plugin the Hard drive.. what its the problem of? do you know sir?

and also i am using right way of assumbling for hardware. But idon't know why is it that hard drive not responding?

And my DATA which is very important for me, i can't want that loss my data which is save on Hard Drive.

Do you have proper and ezy sollution Friend ?


Thanks lot:

& Best Regards,
Hayyat