Hi there!
I'd like to share my experience with the community. If you own an Asus P4P800-X motherboard you could have some problems while installing linux, like getting a loop message "Disabling IRQ" and not being able to complete the installation.

If that's the case, the only thing you can do to get it to work is installing a BIOS update available on the asus web-site.

If that shouldn't work, you can try giving some parametres to the kernel:

linux noirqdebug
linux irqfixup = 0
linux noprobe

If you're really unlucky and you can't get Ubuntu to install yet, try going into the BIOS setup and turn off the OS PandP.

Hope this helps
Bye,
Donato