Some problems with my GPU (Radeon X700)

[LexMK]

Hi

I'm having some problems with a computer I assembled with spare parts.
It's a Pentium D on a 775Dual-VSTA motherboard.
The thing giving me problems is the GPU, a Radeon X700.

I tried LMDE and it starts beeping and locks up. Then, I tried Debian Netinst, installing the OS using another GPU (A broken one that still works if there's only CLI) and tried to make it work with that GPU. I didn't install X and I am using a CLI-only system on that PC now. It works with that other GPU, but when using the X700 it starts beeping again and shows the following error several times and then locks up and I have to shut down using the power button.

do_IRQ: 0.147 No irq handler for vector (irq -1)

I tried upgrading to a newer version of the kernel (3.6) I tried to update the bios, I tried installing the proprietary firmware in Debian but nothing worked.

How can I make this card work?