The disk-assignment numbers may not necessarily match the corresponding SATA or RAID channel numbers. There is no assurance of a consistent relationship between PnP enumeration and the order of the hard disks that are detected during setup. Devices are presented in the order in which they are enumerated. Therefore, the disk-assignment numbers may change between startups. For example, assume that you run Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7 Setup on a computer that has two unformatted SATA or RAID hard disks. In this situation, Windows may present the second hard disk as Disk 0 when you are prompted for the disk on which to install Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7.
RESOLUTION
When you set up Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7 on a computer that has multiple SATA or RAID hard disks, verify the disk drive on which you will set up Windows Vista, Windows Server 2008, Windows Server 2008 R2, or Windows 7 by checking the disk information. For example, on the screen that lets you select the drive for the setup destination, verify the volume name and the available space.