HDD stopped working

[Rebirth]

You should try a clean boot, remove the little batter on mainboard for 5-10 seconds and put off every energy source ( PSU cable for 5-10 seconds ). If the HDD's still not recognized you will most likely want to visit your BIOS via F8, DEL or F12 key via startup keep pressing these keys randomly until you get into a blue menu, there you will have to find your drives and see if everything is there ( if one is missing that either means; - the drive is not plugged in properly, - the drive's energy source is not sufficient, - the drive is permanently damaged )

Also you don't necessarily have to vist your bios in order to do this. You can also type "disk management" into the search thingy of windows ( varying which version of windows you currently use ... ) Take a look if all drives are listed and if all of them are marked as "Healthy"

If your drive is listed there you should get known to the CMD command "checkdsk", too much to explain imho. I guess furthermore google is your friend