Tri-Head PCI card with Altera gpu(?)

I'm guessing you purchased an FPGA development kit. It is not a GPU but a programmable chip where you load a hardware image into it and it takes the form of whatever you designed. So it's not a fixed piece of hardware that has a driver but instead you create a hardware design that gets programmed in (much like firmware) and you build a system around it.

From the description of the board it doesn't ring a bell. The FPGA in the description is very old, from around the late 90s if I remember correctly so it might be difficult to find the documentation and design files that came with the board.