yesterday, i turned on the computer and only the back half lite up,, power to optical drive, no usb keyboard,mouse or monitor, spending the day trying to figure it out, i removed memory and reinstall, and that got it to work. Today my daughter said the power blinked and the computer went back to same state, again i removed memory and reset in same slots and again it worked. both memory and motherboard are about 2.5 to 3 years old