After installing the card, the machine initializes as expected, as does the card (fan test looks normal), but neither the card nor motherboard post. There is no display from the card's output, but I can tell that the machine isn't posting because normal keyboard controls are unresponsive. (Although the lock keys toggle correctly.)
The machine boots using the onboard video and Windows detects the 5770 like nothing were wrong. If I install the drivers, as soon as the files are copied over, the display loses input and the machine is back in the no-post state that occurs when starting it using the PCI-E slot. Furthermore, if I try to boot using the onboard with the ATI drivers installed, the machine posts, but enters the limbo state just as it begins to load Windows (even if Safe Mode is selected).
With the machine using the onboard video and the card installed (without drivers), I opened a tool called GPU-Z which seemed to detect everything about the card normally. Interestingly, the "GPU Clock" read "0 Mhz." I'm not sure if that is normal for a secondary video card that is not in use, but it doesn't seem to be.
Unfortunately, I don't have any other hardware suitable for testing this card. From what I have read, suggested problems include an incompatible motherboard or PSU. Am I wrong in assuming these are unlikely relevant since the card seems to be detected by the system?
Any ideas? If the likely culprit for the symptoms is the card itself, does anything hint at what in particular could be wrong with it?
There should be no incompatibility with that board. 460W is also plenty to power that card, unless you are drawing power to another device and didnt mention it. Based on what you said here, the card is dead. No card will ever idle at 0mhz. The lowest ive ever seen a card idle is 115mhz and that was at 0 load.