1) So I turn on my PC today. No beep, drives, fans, everything running.

2) If I turn off the power and turn it on again very quick. Sometimes my PC will boot to windows and then I can use it with no problem.

3) Another thing is, I tried to restart windows (shutdown option). Windows will shutdown correctly. After that, my PC will not post and got no beep.

I was hoping it is the PSU. But it does look like it is the motherboard (point #3).

Post your specs.

Gigabyte GA-M55PLUS-S3G F13
AMD x2 5000+ black edition
HDD x2
Enermax EG565P-VE
XFX 4870 1GB
LG Blu-ray writer
OCZ DDR2 PC2-6400 Gold 1GB x2

The only recent change is the video card but that was a month ago at least.

Some of the new HD5850 do the same. The card isn't properly powered up at start so the screen stays blank. I've not heard that about the 4870 but it's a possibility.

Test with a different (old) card.

I removed the 4870 and try to use the onboard video. Power up the PC and got the same no beep and no screen (even with the onboard video). Try quick power off and on. I think I boot into windows sometimes but since I cannot see, I dont know. It seems like it is either the motherboard or PSU because they are the oldest components in my machine.

Oh, I cannot warm boot with the onboard video also.

Oh, my bad. I have to click a button on my LCD to switch from HDMI to VGA. So with the onboard video, I can boot into windows successfully everything.

So it seems like it is my PSU.

Clear CMOS Might e a Bad ACPI Setting,
Try a Different PSU, could be bad Voltages.
Try re-seating everything, could be a short somewhere, Attn to the PSU 12V Rail, Power and reset switches

I tried CMOS clear, same problem.

The strange thing is, nothing has been changed for my PC since August (installed 4870) and I have been using it everyday since. Now, it looks like it might be the PSU because onboard video works fine.

What kind of PSU?

I still think it's the card and not the PSU, but certainly easy to test if you can get hold of a different power supply.

Enermax EG565P-VE 535-watt.

Ok, so maybe it is the videocard?

That should be more than enough for the CPU and GFX card. Yes I think it's GFX related, would be most interesting to test with a different 4870 or a GTX285/GTX275 which all require similar power, but maybe not so much peak.

More information. My 4870 got the 3 red lights:

D1601 - Red LED On, shows critical temperature fault

D1602 - Red LED On, shows External power connector A was removed

D1603 - Red LED On, shows External power connector B was removed

D601 - Red LED On, shows critical Core power fault


On my 4870, D1602, D1601, D1603 are on after power up.

Update:

So I ordered a PSU (TX750) because it only takes a week for a new PSU to come and RMA videocard takes at least 2 weeks.

While I was waiting for the new PSU to come, I removed the 4870 and leave only 1 stick of ram and used the onboard video again. I got the same no post problem. And the problem is getting more random (sometimes it took many trials to boot to window.)

New PSU came today and after I installed the new PSU. I got the same problem. Onboard video only with no post. However, the few times I tried, I can start the computer at 2nd trial. Sometimes, if I got no post, I got 1 long beep and 2 short beeps, I googled and it seems to be video problem.

It seems like I have a motherboard problem