MSI K8N Neo2- Power Issue

Question

Howdy folks,
Old problem here, and getting differing opinions from tech support.
If I plug in computer, or turn on at the PSU, all lights and fans turn on without my even pressing the power button, yet it does not boot up. Stays that way, whirring away, until I press the power button and it starts up normally. If I power down after that, as long as I don't unplug or turn off the PSU in back, it works fine.
But, if power gets turned off, either thru unplugging, turning off PSU, or power outage, and then comes back on, the same thing happens. It starts whirring away until I turn it on and then off.
Got 3 vague replies from MSI telling me, "This is normal when the 5Volt standby setting has been enable under the cmos setup. You can disable this feature under the cmos setup." Normal? Most people have no idea what I'm talking about.
Anyway, their last email said it must be the power supply and not the mobo.
Of course, Enermax says it must be the Mobo, because my PSU tester (cheap Compusa thingy) had all green lights.
Unfortunately, I don't have access to another PSU, unless I plug in my old Dell 250W, which i'm worried about frying.
I don't see how it could be the PSU, since it seems to me the Mobo would be the gatekeeper of power to the fans and lights.
Any ideas?

Answer 1

Thanks for the replies.
wwaldo, thanks, but if I understand you correctly, my issue isn't a post problem.
It's that the moment I plug the power cable into an outlet, the machine fans and drive lights all power up.
In my mind, nothing should happen until I press the power button.
It just stays that way until  I press the button, and then starts normally. After that, when I shut down, it powers down just fine, and stays off until I power up normally. It's only a concern to me when I unplug the machine, because everytime I plug it in again, it immediately starts whirring away by itself. It's great if I never unplug it or turn off the PSU in the back, but the fact that it's getting power when it shouldn't concerns me.
Was this the problem you were having?
Regarding the BIOS, I've gone thru each bios update as they've come out, cleared CMOS, changed everything one by one, set things back to optimized defaults before starting over, made offerings to the gods,  promised to be nice to all mankind, and finally I'm just pulling my hair out. Maybe I should just love and accept it the way it is.