my cpu never worked with just my 512 module, although if i had another one in dimm1 it would use the 512. when i took out the 256 it stopped working., so i got a new 512 that was exactly the same except by premium not kingston. its brand new and im sure it would work in my other computer (ill try it to be certain, but it will). anyway, the monitor acts like the computer isn't even on, but the monitor and gfx card work with every other computer in my house. i suppose it could be the motherboard. the monitor light blinks orange which means the power is getting to it.