Oh by the way, memtest can be a bit glitchy on some motherboards, Memtest86+ is often slightly ahead in updates and can be worth trying if Memtest is being picky. I guess you didnt try booting into XP with the ram voltage at 2.1.
PS your timings of 5/7/7/24 should be 5/6/6/18, but thats unlikely to make a difference to the result.
PS your timings of 5/7/7/24 should be 5/6/6/18, but thats unlikely to make a difference to the result.