Hi,
try checking the cables connecting the HDD to the pc in case they are loose or faulty.
Boot into the computers bios by pressing either F2 or the delete key just after the bios beep:
How to enter the BIOS or CMOS setup.
Once in the bios check which drives are connected. If you cannot see the 1TB drive then try swapping the port it's plugged into (after turning the machine off of course). If you still cannot see the drive then it's possibly faulty and needs replacing.
If you can see the drive in the bios then as mentioned above use either a Windows 10 installation disk or a recovery disk/USB to boot into the recovery console and then try the start up repair.