With the ACPI Hardware abstraction layer, you CAN'T really change IRQs in the operating system. And its likely if you change settings in the BIOS, it will just ignore those as well. Moving the card MAY help to change the IRQ, I don't know but again it might well not. ACPI pretty much gives the OS license to do what it wants with IRQs, and you will probably find loads of PCI devices lumped onto one IRQ and governed by ACPI. This is by design so that IRQ conflicts become a thing of the past. But as you have discovered, sometimes it becomes necessary.
Here is how you could overcome this.
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You Do This At Your Own Risk.
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1)Right Click My Computer, Select Manage.
2)Opens Management Console.
3)Select Device Manager.
4)Click on the + next to Computer (Top Icon under computer name)
5)Reveals "Advanced Configuration and Power Interface PC"
6)Right click that, select properties.
7)Go into "Driver" tab
8)Click "Update Driver"
9)NEXT
10)Display a list of known drivers for the device
11)NEXT
12)Click "Show all hardware of this device class"
13)Under (Standard Computers), select "Standard PC"
14)NEXT, NEXT, etc...
15)Reboot and pray.
Hopefully all will be well when you reboot. A number of things will be different. One will be that some advanced power management things DO NOT WORK. Particularly, its likely that if you select "shutdown" from the start menu, it will just shut the OS down, and you will be left with the old message "its now safe to turn your computer off" instead of the actual power going off, i.e. you will loose the ability to power down using software and will have to press the power off button on your case. You may also get IRQ conflicts because you will have lost advanced IRQ management and will instead have to rely on the BIOS trying to do the best it can to make everything work. Try to set "Plug and Play OS installed" to NO in your BIOS if you have such a setting. You might also want to run a "Reset ESCD Data" as well first time round.
Good luck. You might need it.