We need to know if you checked what I posted above so see if the Maximum memory
box is unchecked
or not, a. We would like to help you, but we cannot help you if you do not reply back to our replies with what we requested to see if that may have been the issue or not.
Your motherboard specs
says that it does have a onboard graphics chip. Since you say you are using a graphics card instead, you might also double check your BIOS settings to see if you may have any RAM (memory) still set to be allocated to it. If so, you can just set it to none or zero depending on what option it gives you.