Re: Mixing ram
I'd advise on using just the ddr-400. Mixing memory generally causes stability problems. I'm not exactly clear on what you're saying, but I don't know if both these sticks are the same. Make sure it's the same number of pins (i.e. 184).
C2D E6600 | 4GB DDR2-800 | 9800GTX+ | Asus P5B-E | 150GB Raptor | 320GB 7200.10 | 750W Xigmatek PSU