This eMachines PC was running normally, then froze up mid-session (no obvious errors or problems, just the freeze). On reboot, the Windows login screen appeared, then it froze up again before user could sign on. On all reboots since then, the power light comes on and fans spin, but there's no beep and nothing on screen - no logo, no memory check, no text at all, just blackness. I've never been faced with a machine that appears to have power but won't let you get at least to the BIOS. Could this be a failing power supply? What can I do next??