irq issue causing audio problems?

[mycomputersucks]

ok, so a few months ago, my pc audio started randomly getting distorted. it usually only happens in games but if i exit out of games it will continue to be distorted for all audio. I updated drivers and it didn't help. i thought maybe it was my IRQ settings. both my audio (onboard nvidia audio processor) and a "standard OpenHCD USB Host controller" share irq slot 20. also, my nvidia audio codec shares slot 21 w/ some PCI to USB host controller. could this be the issue? if so, how do i go about reassigning the irq slots? is there anything i should keep in mind when changing IRQ settings? Thanks!