New Computer Will Not Recognize Hard Drive - Won't Boot Up.

NOTE: Before making any attempt to remove or replace any part inside the casing, ensure that the power is off. 

Well, the first thing that might be causing this is your memory card (RAM). Try to remove it and place it in another memory slot on the motherboard. 

To be sure if your motherboard is still in good working condition, remove the memory card and power on the PC. 

You should hear continuous beep sounds. 

If you hear this then your motherboard is fine. 

If placing the memory card in another slot does not work then the problem lies with the memory card itself. You will need to replace it. 

It could also be that some faulting PCI cards are causing this error. 

Try to remove your PCI cards. Normally a faulting PCI modem causes this type of error. Remove it and then power on the pc. 

The processor cannot be faulty but still if you want to check it, remove the CPU Cooler fan. Then turn on the PC. 

Place your finger on the processor for 2 seconds. You should find the processor heating up. Then turn it off immediately. If this works then your processor is good. 
Remember not to leave it ON for more than 5 secs.