its not a hdd issue, if it was then you would still see the bios on the monitor when you turned on the pc.
Its either motherboard, psu, ram or cpu.
Bios post errors are the first step in discovering which is at fault.
Do you hear any beeps?
They communicate a bios post error code which is useful for diagnosis.
Other diagnostic tasks such as measuring psu output with a multi meter and swapping ram sticks are useful but require some kit which you may not have