Unfortunately it looks as though your hard drive has bit the dust. When the drive fails a low level BIOS test (like the short and long tests you performed) it's usually not a good thing. Do you know if you still have a warranty on your computer? If you are uncertain you may be able to check here. If you do, HP will likely replace the drive.
You also have the option of getting a second opinion by our hardware experts. You can start a new post in the appropriate forum here. I would reference this post so they know what has been done so far.
I'm hoping that you have backups of anything critical on your hard drive. If not, I personally know the feeling of losing data and understand how horrible it is. If your data is valuable enough, there are data recovery services that you can send your drive to. They are not cheap but work miracles with dead drives. The one that I've had personal experience with is Kroll Ontrack.
Please let me know if you have any other questions and again I'm sorry we couldn't do more.