I have the same problem - I came back to the computer (which does use standby) and found it impossible to get the machine to run -- pressing and holding the power button just made the CD-RW light blink one, made the fan spin for about a second, and made the yellow/orange lightr behind the power button blink. None of the diagnostic lights on the back went on.
I called tech support and was told to try unplugging all drives and cards and seeing if that made any difference. The tech said that if this did not make a difference, the problem was probably the power supply, and I would need to change it.
I tried unplugging CD drives and hard drive, and also reseating power cables, and that made no difference. So now I will try replacing power supply. (Machine is an 8200 bought with 1 year wty, and is now about 1 1/2 years old.)
Incidentally, the tech said that it should be ok to use a computer store power supply rather than one from Dell -- apparently Dell is no longer using non-standard pin outs on its motherboards and power supplies as it did in the 98-2000 time frame. Also, in trying to figure this out, I read that the power supplies send a "power Ok" signal that the MB must receive in order to initalize. So that seems to be why you get a blinking light, but no boot, if the power supply fails.
Please let this board know if changing the power supply solves the problem.
I have the same problem. I have a DELL GX 280 desktop and the power goes off after 10 minutes. The power button starts to blink orange. I have checked standby, hibernation, and all of my power management settings and turned them all off. Still having a problem.
I went through my event logs and saw nothing that would indicate an abnormal shutdown due to a hardware or software problem.
Does Dell have any diag software that I can run to find my machine state? If so, where can I get it.