This morning I powered on my PC. It worked fine. I just entered the password to log on to Window 7, but then I fell asleep so I went to take a nap. When I woke up the PC wasn't on. I tried to power it up, but nothing happened, although the mainboard light is still on.
Suspect it was a mini power surge, I unplugged the power supply from the wall for 15 minutes, but it was still the same.
I found some answer for this problem in homebuilt section, but they are all about first installation, while mine was working fine for 2 months.
Well, first, the motherboard LED really does not mean much. The small, always on, standby power supply inside the PSU powers the LED. It has nothing to do with the main circuits that provide operating power to the PC.
About all it does is tell you that the system is plugged into a live wall socket and the PSU is physically switched on.