You can either change it from within Windows' (assuming you're using it) Device Manager, or your BIOS. Consult your documentation for instructions to do it from your BIOS.
When it is first starting up > hold down F8. That should get you into a dos screen. Use your arrow keys to go over to the 4th (I think) tab. Open it & look for PCI settings or such. In there will be a window with your IRQ assignments. You can change them with the arrow keys.
It has been awhile & I can't remember exactly which tab, etc. but I know that is how I change mine.
OK, I get PCI IRQ (? I think that that's what it was) #1, 2, 3 , and the priority selections are IRQ #9, 10, and 11. What do I select? It's currently on Auto.
Really, you should use Windows' Device Manager. Just find your video card, right click to properties, and then the resources tab. You can change it there, and it's much easier