Would you please let me know the model number of the memory you are using?
It looks like the motherboard can handle up to 16 GB of RAM; however it needs to be DDR3 1066 and 1333 MHz only, since these are the memory speed processor handles.
You may want to run some basic troubleshooting steps such as:
- Test the system out of the chassis, minimal configuration (Motherboard, processor, power supply, 1 memory stick and video card)
- Remove the CMOS battery and leave the system without it for about an hour. Then put it back on and restart the system.
- Start adding one component at the time until you find the conflicting one.
- Swap components to narrow the issue if possible.
- Any additional troubleshooting provide by HP.