Hi. I've got a situation that seems a little odd to me. My system has a Gigabyte motherboard (GA-880GM-UD2H) with a PCI-E slot for the graphics card. I have several Nvidia cards: an GeForce 8600 GT, a GeForce 6800, and several older Nvidia cards. If I put in the 6800 or any of the older cards, the system boots fine. But if I install the 8600, the system won't boot at all. I mean zero response - no fans, beeps, nothing. Then I put the older card back in and it boots right up.

My first thought was maybe the power supply wasn't strong enough. But I have a 450W installed right now, and I would think that would be enough on my little system.

My guess is that the graphics card itself is bad, but I was hoping for a second opinion, or other insight. I was hoping to be able to use the 8600 because I've read it has better nouveau support, and I prefer using the free drivers.

Do you have the chance to test the video card in a different system?
From what you describe it sounds like a faulty card. But if you prefer free drivers anyways I would just use the inbuilt Radeon HD4250 video chip, the open source radeon video driver is far better than the nouveau driver and should support your card just fine.

Unfortunately, the Radeon cards require non-free firmware (see "binary blob controversy"), which has been removed from the libre kernel which I use.

Update: The same problem has now occurred with the 6800 Nvidia card. I went to eat dinner, and when I came back the computer had shut itself off, and would not boot. I remove the 6800 and it booted right up. I'm beginning to think there is something wrong with the motherboard itself, evidently related some how to the PCI-Express sub system.

As has been stated, it could be a bad card. Try it in something else.

Another possibility is current drain (a short circuit). The power supply will struggle, the 'power good' line won't toggle and nothing happens.

The other possibility is a speed thing. To go faster, the electronics needs to be at lower voltage and clocked faster. Different generations of the same slot have different characteristics, and it sounds like the newer ones aren't compatible with the motherboard. You might be able to sort it in the BIOS.

Power consumption shouldn't be an issue with the 8600, may be with the 6800.
Also, the AMD 880G chipset supports PCIe 2.0, which is backwards compatible, so compatibility shouldn't be an issue, too.

I wasn't thinking power consumption, I was thinking blown devices.

I have no real knowledge of modern Nvidia cards, but I do know a lot about blown hardware!