I'm having problem with my PC. For some reason my OS and BIOS do not recognize the memory correctly, although it used to recognize it. I have 12GB but only 8GB recognized. I have Rampage III motherboard, which supports up to 24GB.
I'm running it on Windows 7 Home Premium and I have 2GB × 6 sticks.
If I use CPU-Z to verify it, and it shows 12GB for the memory.