Computer won't Power On (Tried the usual fixes)

[matthewr77]

Specs:
eMachinge T2885
2.8 Ghz Celeron
80 GB HD
512 DDR SDRAM
Windows XP (home edition) SP 2
Intel Extreme Graphics 3D
Intel Desktop Board D845EPI/D845GVSR

Issue:

Computer will not Power On

Circumstances when it happened:

Windows had just opened up the desktop.
I closed my AVG Antivirus software and opened a Word Document.
I had just previously closed Skype autostart and printer icon in system tray.
(All usual events that had previously caused no problem)

What happened:
AVG popped up to confirm I wanted to close it while the Word opening box displayed.
Then the cpu powered off (no noise, blank screen), but the LED stayed on.
(I had previously had an issue with the computer not wanting to come out of standby no matter how many buttons I pressed or how hard I pressed them )

What I've tried:
I tried pressing the power switch.  Nothing happened, it stayed on with cpu off.
Unplugged and replugged in the Power Supply.  The LED has stayed off since...
Switched Power supply.
Reseated all connections except Processor.
Tried looking at power on button, but it is enclosed and I was unable to look at it.

Additional Info:
On both power supplies a green indicator light on motherboard stays on while plugged in.
When reinstalling the old PS it made a high pitched whine not noticed before.
The Power Supplies are set to the correct voltage.
The Power Supplies make a quiet hum, but no fans spin.
At one point after unplugging/replugging the first PS, on holding down the power button I heard something sound like it was wanting to start (like a jet engine), but I've been unable to reproduce the sound.

The power still does not come on, nor does the power LED on the front of the cpu.

[Dias de verano]

eMachines

uh-oh!

When reinstalling the old PS it made a high pitched whine not noticed before.

uh-oh!

At one point after unplugging/replugging the first PS, on holding down the power button I heard something sound like it was wanting to start (like a jet engine), but I've been unable to reproduce the sound.

uh-oh!

The power still does not come on, nor does the power LED on the front of the cpu.

unfortunately eMachines are well known for having defective power supplies and motherboards. Consider replacement.

[matthewr77]

So...I should get a new power supply or motherboard...or both?

I'm still a little confused how one of them could be an issue if the LED on the motherboard is still lighting up.

Would it just be an issue of insufficient voltage?

I have a 3rd PS that I will try to see if my other "new" one is also defective.

Thanks.

[Dias de verano]

I meant, get a new computer. The LED lighting up means nothing. Try a new psu first.

[Carbon Dudeoxide]

Try a new psu first.

Switched Power supply.

Hmmm...he said he did.

What about the Motherboad Battery. Do you think that may have something to do here?

Matthew, I also just wanted to say that your post has the best layout I have seen in quite some time. 

[Dias de verano]

Try a new psu first.

Switched Power supply.

Hmmm...he said he did.

I was answering this

I have a 3rd PS that I will try to see if my other "new" one is also defective.

[matthewr77]

Thanks for the compliment. 

I also recently tried a 3rd Power Supply and pulling out the CMOS Battery for 10 min. as per suggestion in the motherboard's online manual.

I recently pulled the motherboard completely out and I'm planning to go get a new one.

Does anyone have any concern that this will not work or that I am spending needless money?

[matthewr77]

The new motherboard finally came in Thursday....however...

I tried installing everything the way it was supposed to be, but it wouldn't turn on.  After trying to put the Power SW/HDD LED/ Power LED in different places the Power LED sat there turned on (I hadn't pressed the button) and when I did press the button the computer lurched to life for the first time in a month.  The monitor came on and a new/different startup screen was displayed.  The windows loading screen came up and as soon as it cleared the screen to show the log on display it just stayed blank.  Since then I have been unable to get the screen to show at all.

Important info:
There has also been an ominous red blinking light on the motherboard that flashes as soon as I plug in the computer. . .
(There is also a green light that stays on which I'm not worried about)

Any ideas on how to finally get my computer working again?

I am pretty sure the motherboard is the exact same as the original.

[matthewr77]

UPDATE:
The new motherboard is working.  I think the blinking red light is just showing that it is on (I was incorrect before stating it is always on when there is power).  The issue ended up being with my wireless card that I had not used in a long time which was causing system instability.

Thanks to everyone who helped.

My only issue now is with a lack of audio which I will be posting in a new thread...