Went out and bought a Radeon 4850, stuck it in, wouldn't boot. Turned on for just a split second before turning back off. Thought it was probably the 300 watt power supply so I went out and bought a 650 watt power supply by Antec. Installed that. Same thing. Yes, it's getting juice from a PCI-E power cable, yes, the main graphics bus is set to PCI-E x16 in the BIOS and yes, it's in as far as it can go. Though I thought it felt like something was keeping it from going in all the way. There are no visible obstructions but perhaps that L-shaped face plate is coming in contact with the case metal beneath the motherboard?

The computer boots without the card but still turns on for only a split second if it is in the PCI-E slot.

Thanks in advance.

Hmmm have u tried popping the card into someone else's system to see if the same problem occurs? If so then the card is faulty so then u could send it back. Does ure system run fine with any other card that u have? If it is running fine then its obvious whats the problem. Your power supply is fine for this card. And you definately woud not have been able to run it with the 300watt u had before. Lets just hope u didnt molest ure motherboard while trying to run it on that power supply.

I think the motherboard is probably fine because it still works when I take the card out. I'm now trying to figure out what not powering on at all is symptomatic of: broken video card or not being plugged in all the way. I'm hoping the former because I'll never be able to make another one fit anyways without modifications (give HPs design team a pat on the back) and I can always just exchange it.

Unfortunately I don't know anyone who has a PCI-E slot, either.