My HP will not recognize sata hard drives - HEWLETT-PACKARD HP Pegatron M2N78-LA ASUS OEM Violet6-GL8E NVIDIA 9100 AM3 Motherboard (610074079576)

One bad lead can cause a computer to continue on a cycle or to shutdown or fail to detect/ boot up a computer hard drive

Test all leads that attach to your hard drive including electrical extensions,IDE,SATA

the leads from your ((motherboard to your hard drive)) make sure they have a secure connection and are not faulty or just replace them there probably old and faulty
make sure all leads that are attached to your drives dvd\cd 3 1/2 inch floppy have secure connections and are not faulty even the electrical extensions or just replace them they could be faulty a computer needs its connections to continue its cycle and to have an end so any faulty leads will end up with a computer error or
Restart your computer with the XP Setup disk in the CDROM drive.
If you are prompted to press a key to start the computer from CDROM, do so quickly. Otherwise it may try to boot from the hard drive. After a few minutes, you'll see a prompt to press the R key to start the Recovery Console. When Recovery Console starts, it will prompt you to enter a number corresponding to the Windows XP installation that you need to repair. In most cases, you'll enter "1" (which will be the only choice). If you press ENTER without typing a number, Recovery Console will quit and restart your computer. Enter your Administrator password. If you don't enter the correct password, you cannot continue. At the Recovery Console command prompt, type fixmbr and then verify that you want to proceed. Your damaged MBR will be replaced with a shiny new one, and you should then be able to boot your system normally. In some cases, you may need to repair the boot sector in addition to the MBR. If your system still doesn't boot properly, repeat the steps above, but issue the fixboot command instead