Hello,
1st check if BIOS can the HDD, if not then it might be HDD problem or motherboard, so try to connect the HDD in other system, if it works then it is the motherboard otherwise it is the HDD, also change the cable and make sure the power cable is connected properly.
2nd if the BIOS can see the HDD then connect the HDD in another working system as slave, and boot that system to see if you can see the partitions and the partition table in the defected HDD, if you can't see them then it is a corrupted partition table problem, I'm afraid you have to install every thing from scratch, if you don't have backup of your data then you may try with some recovery tools before doing anything to the HDD.
3rd if you can see the partitions then it is a master boot record problem (easy) , backup your data as a first step, then use windows CD to restore that sector.
