Since you have two hard drives, I'm going to assume that your computer is a desktop.
Turn the power off.
Take the cover off.
Blow out all of the dust in the computer.
Remove and reseat, on at a time, each and every connector and each and every add in board.
Leave the cover off.
Turn on the computer.
Are all fans running? Yes or No.
If possible, put you hand on the top,side, or bottom of the defective drive. Feel any vibration? Yes of No.
Disk unit working now? Yes or No.
I'm looking forward to three answers.