I have an HP Pavilion a6430f that is hanging at POST. It takes approximately 5-10 minutes to get past POST, at which point it loads Windows (Vista).
This system has an AMD Phenom 3-Core processor, approx. 4GB of DDR2, and two 320GB hard drives. Here's what I've tried so far:
1. This issue occurs when everything but memory, CPU and motherboard are present and everything else is disconnected.
2. I have cleared the CMOS, removed the battery, as well as loaded defaults in BIOS.
3. I have tried several different boot orders, have disabled the floppy drive in BIOS, and moved it to the bottom of the boot order.
4. I have tried a different power supply. The original is a 300W Bestec, I have tested with both a 350W Antec as well as a 550W Antec.
5. The memory has been thoroughly tested with a very, very heavy duty memory testing program that runs outside of Windows (not memtest86).
6. I have cleared any debris or dust from the fans and heatsink to remove the possibility of thermal issues.
7. The system, when fully assembled, passed a 4-hour stress test of the CPU, HDD, Memory and video card.
8. I have tried to locate a BIOS update for this system (Current version is 5.11), however HP has none listed, and the HP Advisor program does not offer any inside of Windows. I looked up the motherboard model and found a specific update for the motherboard (version 5.49) from HP but it's installer says that it is not compatible with the system.
More interesting details:
To get to the BIOS, you must repeatedly tap F10 until the 5-10 minute hang has ended, at which point it will accept your pressing of the button.
In BIOS, I turned off the full screen logo. During POST, it lists the basic information about the processor, and hangs for a long time, until flashing the CPU speed information, memory information and hard drive information all at once, after which it continues with normal boot.