As you install the OS. So follow the directions above that I provided and you'll be able to initialize the RAID Array as you install the OS.
With Windows Server anything when the [b]First Blue Screen Appears[/b] press the [b]F6 Key[/b] and wait till you are prompted to insert the Raid Driver copied to the [b]Root[/b] of a Floppy. Root means directly to the Floppy [b]Without[/b] being in any folder. so that when the Drive looks at the Floppy all it sees is the RAID Driver.
After you have the RAID Driver installed the Setup of the OS will be included with the RAID Setup. You'll configure the RAID before you start to install the OS but after the HDD's are Formated.
As to the exact method of doing this it depends on the actual Hardware Controller that you have in place but they all need the Drivers Installed before you start to install the OS. ;)
Col