Within the past 2 weeks, a problem has come up which I believe could be my PSU, but I wanted to get some opinions or comments about this. My computer power is connected to a power distribution switching unit which gets its power from my UPS and then I switch the power ON to the Computer, Monitor and Speaker Amps. My computer normally only has the small Green LED near the Bios Battery that illuminates when I apply power through this switching unit. Then I depress the computer's power button to turn it ON. Lately, as soon as I apply power to the computer, it comes ON without me depressing the front panel power button. Could this be a sign that my PSU is on it's way out? This happens randomly not all the time. What say anyone?

The green led.

That situation is normal. In fact, if you had read your mboard manual throughly it probably tells you about it.

The green led on the mboard is on as long as the PS is working and is connected to the mboard properly, and there is live AC to the PS. ATX power supplies are always powering ATX mboards in some places as long as live AC is being supplied to the PS, even when Windows is Shut Down or in Standby or Hibernate modes, or even if you have no drives at all atached to the mboard.
The green led being lit up is there to warn you there is DC power present from the PS to the mboard. Whenever you make any changes to connections or components inside your case, you must remove the live AC to the case/PS to prevent the possibilty of you damaging something - e.g. if it is connected to a power bar, turning off the power bar removes the live AC but the case is still grounded through the grounded power cord.
....

"Lately, as soon as I apply power to the computer, it comes ON without me depressing the front panel power button."

That CAN be a sign of a defective PS but it usually isn't.

That's much more likely to happen if the switch on whatever you are turning on is producing electric/electronic "noise" as you switch it on and is nothing to be concerned about. It tends to happen after having used the switch many times. I have a power bar switch that occaisionally does that.
The only cure is to try cleaning or replacing the power switch, or replace the power bar.

There is a setting in the mboard bios Setup that determines how the mboard reacts to power off and what it does after power is restored. Usually that setting is set by default to not auto boot the computer when power is restored, but if the switch on the power bar or whatever produces "noise" the mboard may boot by itself despite that.
Some mboards have that Setup setting set to auto boot when power is restored by default, but in that case it would always boot when you turned on the power bar.
.....

On the other hand, if there is some other reason you think the PS is defective.....

Failing power supplies are common and can cause your symptoms.
Check your PS.
See response 4 in this:
http://www.computing.net/hardware/w...

Tubesandwires: Ok, thanks for your response. Ok, let's look at it in this manner. I connect the power cord from the tower to the wall outlet and my computer turns ON. This is what is basically happening. It is not normal to plug in the power cord and have your computer turn ON with depressing the Power button on the face of the computer. Only difference in my case, I have a power distribution unit to basically switch the power ON as if I was plugging it into the wall. For 4 years now, this was not the way it turned ON. I always had to depress the power switch on the computer's front panel.

"I connect the power cord from the tower to the wall outlet and my computer turns ON. This is what is basically happening. It is not normal to plug in the power cord and have your computer turn ON with depressing the Power button on the face of the computer."

Have you changed any bios settings, or replaced the cmos battery, or set bios settings to defaults, or flashed the bios since it last behaved as expected? Check the setting in the bios Setup explained above (note that I just added more to the post).

Ok, here goes. If you connect your computer's power cord to the wall socket (115vac), your computer should not normally start up and boot. After plugging in the power cord to the wall, you should be able to then go and depress the Power On button to start your computer, right? Well mine starts booting when I basically connect the cord to the wall socket. Only in my actual case, I use the power distribution switching unit to accomplish the same thing, which now that I think about it, it is a dumb way of applying power to my computer. I have switched PSU's and the problem still exists. In the 5 years that I have been powering up my computer in this manner, I may have screwed up some caps or circuit components on the mobo. I replaced the CMOS battery today and rechecked my Bios Setup per the manual. All looks normal. I have decided to leave the power ON the computer rather than switching it completely OFF. It's a work around, but after 5 years it's still running fine. I don't think I will continue on this problem anymore. I really appreciate your input Tubesandwires. My poor old mobo has one hard drive in the grave. Thanks again.

Much of what you said in response 4 you already said in response 2 and previous - there is no need to repeat it.

"If you connect your computer's power cord to the wall socket (115vac), your computer should not normally start up and boot."

Not necessarily true.
It depends on settings in the bios Setup, and sometimes on whether or not you have a "noisy" switch in whatever the computer is connected to. If the PS itself has a switch, it can be "noisy" too, but that's not likely if you haven't fiddled with it (you could try toggling it on and off several times if you have one).

"I replaced the CMOS battery "

Probably completely un-necessary. Coin shaped cmos batteries normally last at least 5 years, and if your battery was weak or dead, you would be getting a "Cmos Checksum Error" or similar every time you booted after removing power to the computer, and the Time and Date would be set to defaults.

Changing the Cmos battery sets all the bios cmos settings to defaults.
Older bioses by default are usually set to NOT auto boot the computer (e.g. Stay Off) when power is restored to the system, but I've seen some newer bioses that have that set to auto boot by default - check that setting.

If you tried another PS and the situation didn't change it's obviously not caused by a faulty PS.

It's extremely unlikely you have a bad capacitor problem - if you did the system booting by itself would not be your only symptom. The capacitors are usually larger cylinders on end - if you have bad capacitors you will see the tops of some are bulging and may be opened up, rather than flat and sealed, and they may have yellowish or brownish fluid or dried deposits of the same color on them or at their base.

It's possible but unlikely something you did damaged circuits on the mboard to do with this, if you didn't always remove AC power to the case/PS when you fiddled inside the case with connections or components. If you have never overclocked it's extremely unlikely you could damage capacitors.

If the bios setting is correct and that doesn't help, and if you can't find evidence of anything else being wrong, if this booting by itself is the only thing wrong, you shouldn't worry about it.

It sounds to me like an incorrect BIOS setting.

"rechecked my Bios Setup per the manual"

Why exactly does that mean? The settings printed in your manual are generic...they cannot possibly be correct for all the different hardware combination possibilities. You should always custom configure the settings to match your hardware. The setting you need to check would be in the Power Management section...look for something like "power-on after power failure" & make sure it's disabled.

Tubesandwires: I did get a CMOS checksum error when the computer booted up before depressing the Power On switch. Sorry that I didn't mentioned that. Right after that, I went into the Bios settings and reset the readings to what I had originally set up. And yes, Jam, you are right. I basically have most of the settings memorized so I set them up almost to the manual, but there are a few settings like FSB is defaulted to 100Mhz and it should be 133Mhz, I also have to disable USB and Audio because I have an extended USB PCI board and a Creative sound card. There are other various settings that match what equipment I have so all have been re-configured as before. BTW, my CMOS battery read 2.5V. The new one read 3.15V. In the almost 6 years that I've had this computer, it has never, until a couple of weeks ago, booted up just plugging it into the wall without depressing the Power button. That's what started all this. Jam, you are totally correct in what you say about my Bios setup. I rechecked the Power Management portion and everything appears to be like it was before or has always been. I do not see any changes out of the ordinary. Well, the good thing that came out of all this is that I totally had an empty case, cleaned it out, cleaned all the connectors, rerouted all my cables and neatly ty-wrapped them to the case, cleaned and blew out all fans, including the PSU fans and all filters are new, again. Computer runs fine, but this time the power, by way of my UPS, is always applied to the computer. No more switching it OFF when I am done. I really appreciate you guys inputs, honest. Have a good one.

What is your mboard make and model?