Just plug in a 4gb+ UBS flash and format primary, then load the Win7 DVD files into the root. Reboot the target computer and tap F-key for Boot Menu given on first screen. Flash will be listed under HD's.
I think your problem is the RAID. We are seeing a lot of them refusing install and cannot get around it. It would be best to abandon the RAID config since it is dated technology anyway with drive imaging built in to Win7.