Is it a motherboard or graphics problem?

Hello,

I've had an issue with my ATI Radeon HD 5870 card over the past half a year or so - namely, that it doesn't want to work. It worked before, but upon upgrading my rig (due to failures from other parts), something seems to've gone wrong. I've tackled the problem multiple times with mixed success, but the potential of my current (onboard) graphics failing has spurred me to further action.

In short, I cannot get the card to be fully detected or display graphics. I can plug it into my PCIE slot, complete with power, and it'll power on, get warm and all that good stuff. If I plug my DVI cable into it, though, nothing will display on the monitor. This happens even if I go out of my way to disable or uninstall my onboard's Intel HD 3000 drivers. I have tried unlocking my monitor's OSD and flicking through the inputs/sources, but nothing will display.

After returning the DVI cable to its original position (note: the card is still in and powered) and going into the Device Manager, I scan for hardware changes and see a Standard VGA Graphics Adapter. According to Windows, its drivers are all up-to-date (circa 2004 or so) and I should just restart my computer, though it does tell me I have a Code 12 error (not pictured; see next link). If I do so, I reach my main impasse: my computer no longer boots up until I remove the card. I suspect this because I cannot get a display from either the onboard or 5870, my USB devices will not power on (such as my wireless headset's receiver) and the PC will power down immediately on pressing the power button.

If I try and install the graphics card's drivers before rebooting, the installation program recognizes the card's correct series. However, the Code 12 persists - even with the onboard disabled. Upon rebooting, I encounter the same no-boot problem as before.

The motherboard is considerably newer than the graphics card is, but it comes with a lot of random tag-along programs from Intel that might be interfering with the card. Because of this, I've no clue which side the problem lies on, and I currently only have enough money to replace one of the two parts - if it comes to that.

Finally, a DxDiag of my current working hardware, if it's of any help.