Load your RAID drivers on a bootable floppy or USB drive.
Go into the BIOS and enable RAID, and make your optical drive the 1st boot device.
Then you should see an option to access the RAID BIOS. Set up your array.
Save and exit
Insert your OS disc and restart
Start the format/install process. At the very beginning watch for the f6 prompt to install RAID or 3rd party drivers. Hit f6 to select your RAID drivers.
The RAID drivers will install, and then windows will continue installing on the array.