I'm running a Intel Core 2 Duo E7400 on a ASRock P43TWINS1600, with a set of Kingston KVR1333D3N9K2/4G ( Kingston Technology Company - Kingston Memory Search - Search Results for: KVR1333D3N9K2/4G ) My problem is that in BIOS I'm not able to choose 667 MHz frequency for the RAM, only 400 and 533 - and yes, I have them installed in the DDR3 memory slots. I'm sorry if I've left out any useful information; I'm not that experienced in these kinds of forums.