Power issue? mobo issue?

[matrix86]

We went away on vacation for 2 weeks. I unplugged my computer, but my father-in-law left his in (plugged into a surge protector). We come back from our vacation and his computer won't turn on. I take it downstairs, plug it in and as soon as I plug it in, the light on the motherboard comes on and the fan turns on, but that's it. No post, no running hard drive.

I tested each stick of RAM individually with no results. In order to turn the computer off, I have to unplug it. The power button is orange (should be green unless Dell changed that for some reason), and the hard drive light stays on (though it isn't running). No matter how long I hold the power button, nothing happens.

His computer is a Dell Optiplex GX270, service tag 8R70H31. That's all the info I can give ya.

EDIT:
forgot to mentioned that I checked the mobo for any burn marks and didn't find anything. And everything is plugged in good. Took it all out and plugged it all back in.

 

[matrix86]

So far from what i've been able to tell, it appears to be automatically turning on and booting into stand-by mode, and just won't come out of it.

 

[westom]

Go to the Dell website support page. Enter your service tag number. What you need is all found on that page. Under manuals, you will eventually read this:
http://support.dell.com/support/edocs/systems/opgx270/en/ug/solve.htm#1235408

It says what your orange light means. On the back are important diagnostic lights.

You may also have a chassis intrusion switch.