Usually there are something wrong with OS but let’s double check everything first:
Firstly power off your system and unplug all cables from CPU and open the case.
Now see that whether your HDD wires are connected properly or not, if not then connect them properly and close the case, connect all cables and start your system and observe whether the issue will be resolved or not. If not then this is definitely a software issue. Your OS probably corrupted.
Now you’ll have three choices:
So firstly try to repair it through system repair disk or OS disk.
If above one not works then if you have a System Backup then you can restore your computer state to that earlier time state.
If nothing works then unfortunately you have to perform a fresh Install.
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