With the power off, open the case and check the drives cables (data and power) to make sure they are in all the way. Be sure to touch the case often as you work inside it. lso follow the data cable down to the motherbd and make sure that end is in good.
Next power up the pc and go into the bios, which usually means pressing the Del key when prompted to on your screen. In the bios, it should list your drive. be sure it is selected as the primary boot device.
Saving and exiting will cause thepc to reboot. Hopefully all is well and windows will begin loading.
if the drive was not detected in the bios, put a finger on top of the drive and see if you can feel it vibrating . It should not be making a repeating clicking sound. (click of...