I have a Dell Optiplex GX620 minitower that was working just fine until a couple of weeks ago, no problems at all. One day, however, it wouldn't power up; instead of the green power light, I got a blinking amber light. I tried unplugging everything from it and letting it sit for a bit, but it still won't power up, and it still gives me the blinking amber light. I have checked the chassis intrusion switch, and I have replaced the motherboard. I've also verified that the power supply is functional. We did try unplugging the memory and video cards, and it still won't work. We also checked that all of the USB ports seem to be fine. We also tried a different power cord. None of the diagnostic lights come on at all. Any more ideas?