In the BIOS
This is probably the best place to check to change your IRQs.

On Windows
Open the device manager, right click a device and click Properties. Then go to the Resources tab.
This allows you to see/change the IRQ (Levels):

On Linux
Open up a shell and execute:
cat /proc/interrupts
This for example, gives:
CPU0 CPU1 CPU2 CPU3
0: 187 0 0 0 IO-APIC-edge timer
1: 39922 0 0 0 IO-APIC-edge i8042
7: 0 0 0 0 IO-APIC-edge parport0
8: 4 0 0 0 IO-APIC-edge rtc
9: 1 0 0 0 IO-APIC-fasteoi acpi
12: 846774 0 0 0 IO-APIC-edge i8042
14: 105048 0 0 0 IO-APIC-edge libata
15: 0 0 0 0 IO-APIC-edge libata
16: 1069722 0 0 0 IO-APIC-fasteoi libata, uhci_hcd:usb4, nvidia
17: 105382 0 0 0 IO-APIC-fasteoi eth0
18: 83040 0 0 0 IO-APIC-fasteoi uhci_hcd:usb2, libata
19: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb1, ehci_hcd:usb5
20: 474168 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3, ohci1394, ra0
21: 10117 0 0 0 IO-APIC-fasteoi bttv0
22: 594327 0 0 0 IO-APIC-fasteoi HDA Intel
NMI: 0 0 0 0
LOC: 1754492 1545836 2085855 1878596
ERR: 0
MIS: 0