Computer help forum: Help Please! Hard Drive Not Recognized, Frozen HP Screen.

Please help me. I cannot get my computer to recognize the hard drive or perform a system recovery. It is stuck on the HP screen. Here is all the information:

The process of dying:
My computer started freezing while playing games and surfing the internet. The freeze happened periodically over two days, but I was able to restart and enter Windows normally. Then the computer started getting stuck on the opening HP screen and Windows was not loading. I ran Diagnostics and the computer froze. I ran System Recovery from the hard drive but the computer gave me error 1002. The computer became unresponsive and was permanently stuck on the HP screen every time I restarted it. So I purchased a new hard drive and ordered system recovery disks.

The process of trying to rebuild:
The BIOS does not recognize the new hard drive, nor does it recognize the old one when I plug it up. Trying to run the system recovery disks gives me the message to insert boot disc and press any key. This message repeats itself over and over despite having the discs in the drive (I have used both + and - boot discs, and set the BIOS to boot from CD). The computer is still stuck on the HP screen but I can enter BIOS sometimes. The monitor randomly does not come on during some restarts, but when I re-seat the video card and RAM it works again.

My thoughts now:
I'm starting to think maybe the motherboard is the issue. I just don't have money to throw away on random parts in the hopes that something works. I have unplugged and replugged everything, tried different cords, etc. WHAT IS WRONG? And HOW do I fix it?!! Please help.

Specs:
Paviolion Elite e9120y PC
AMD Phenom II X4 910 Processor
8 GB DDR3 Memory
Corsair 600 watt Power Supply (upgraded last year)
AMD Radeon 6700 HD Graphics Card (upgraded last year)
Old Hard Drive: Western Digital WD Caviar Green 1TB
New Hard Drive: Western Digital WD Caviar Black 1TB