RAID1 configuration

I have two 300Gig drives that I need to create a RAID1 with a 50G C: partition and the rest for the D: partition.  How do I go about this?  Make one virtual drive and partition it out?  Do I do that during the OS setup or run the Dell Installation and Server Management cd?  I had installed everything, including the OS before I realized I did it wrong so I ran Setup (F2) at the next reboot and recreated the virtual disk and now it is initializing the drive.  This is in a PE 1950

Thanks,

KBeau