Found this link in another thread:
I've tried everything to try and fix the missing memory issue, except this. I did go ahead and buy a new motherboard after being fed up, then I found this video.
Here's the problem: I can't find this setting in the bios anywhere. I can't even find anything resembling it. That asus bios looks like it has a lot more features.
The board that I have coming is an Asus P6X58D-E, and it should be here wednesday. If I can get the problem resolved by then, I'll just go ahead and return it. Assuming I can find this setting somewhere.