paaji

i am new here ok my question is that i have asus p4p8x and i want to upgrade the memory on that one. So i bought 256 3200 400mhz azen memory previously i had 256 3200 400mhz samsung memory. So when i installed the both memories together computer doesn't boot. i put each one at a time computer boots but if i put together it doesn't boot. so took both memories and put into a another computer together with amd cpu it works but not on my computer. Which means memory isn't bad cause it works if i put one at a time. I don't know about the dual and single memory cause if boots together on the other computer with different motherboard then it should work. Maybe this might be the cause but i have no knowledge about it. Another thing i did is put into 1 and 3 and 2 and 4 slots to check out but no luck so i returned the memory and bought another brand which is GB micro and same thing happens. I updated the bios but not sure whether it is right one. I don't what is wrong so please help