IRQ assignments for PCI is it possible?

Hi,

I have a ASUS P8P67 mainboard and it has 3x PCI slots where I try using a Creative X-Fi Platinum PCI soundcard.
My system is Windows 7 Pro x64.

Why is there no possebility in Windows 7 to change the IRQ as some IRQ are available like 3,4,5,6 & 7, if the bios assign them it seems to me the bios is quite stupid to make IRQ conflicts however the drivers schould have IRQ Sharing compability which seems not to do it's job very well.

Is there any chance I can assign the IRQ's manual by some mabe hidden bios settings?

Thanks in advance for your input!