go into bios and change the multiplier to x4 and then boot ,,,,,you must have the mem installed in pairs they have filler things that should have come with your mother board shove those in the vacant socket,,,,if you have the p4c follow the scimatic and instal one stick in each of the two recipticals with a fake rimm next to it,,,there is supposedly a downloadable flash for your bios to get rid of the problem of your bious not auto recognizing the sticks,,,,,,,,i personaly just leave my 1066 ecc mem at x4,,,,,,,,