should i run ddr370 at ddr400 speeds?

I have some Corsair XMS 512mb stick of PC3000. should i change the cpu/memory ratio from 3:5 to 3:6? that would be 400mhz then right? what should my timings be at then?

Thanks!!!

The question is not should you do it, but can your RAM handle it? You won't hurt it, if it works, it works, if it doesn't, it doesn't. Try the slowest timings first, and if it'll do it, see if you can use faster timings.