Directions only for Simono -
Before you install the driver, go to device manager.
Under system devices, should be something that says CPU to AGP controller, possibly preceded by your chipset manufacturer's name. For instance, mine is "Via CPU to AGP controller."
Right click on that and choose update driver software. Then browse my computer. Then let me pick. Choose PCI standard PCI-to-PCI bridge. Then next and let it install.
Now install the video card driver as before, using my .inf.
If it works, wonderful. If not, revert the CPU to AGP bridge back to the default that it was. Good luck.