I setup a virtualbox in Ubuntu12.04 and setup a win7 in it.
1. Win7->Settings->Storge - Choose a virtual CD/DVD disk file(iso file)
2. Set the root seq is CD/DVD first in Settings -> System
3. Start Win7
Unfortunately, 0xc0000225 boot error in Virtualbox occurs.
Resolution: Before #3, we need to enable IO APIC in Settings->System in virtualbox Win7