In some setup's the RAID-1 ( morror ) can be "broken" in a safe way.
I think your RAID chip is based on a Promise controller, so the following
might apply to your mobo.
The simplest and easiest way to break a RAID 1 mirror on the 1200A is to have only one of the drives in the mirrored pair connected at startup time or boot time.
This will force the 1200A Raid card to believe there is a broken RAID 1 and will display an alternate startup screen that will allow the following options:
Broken RAID 1 - Critical Status - A disk member of a mirroring array has failed or is not responding. The array is still functional, but fault tolerance is disabled.
1.) Power off and replace the failed drive
2.) Destroy the Mirroring Relationship
3.) Choose a Replacement drive and Rebuild
4.) Continue to Boot
When option number two (2) is chosen, it will delete the RAID table information from the drive that is currently connected to the 1200A RAID controller. This operation will make that drive appear as a stand alone drive that was never part of a mirrored pair.
Note: This operation must be run on both drives that were part of the mirrored pair, to erase the RAID table information on each drive.
CAUTION! Do not use the " Delete array " operation through the " Ctrl+H " Bios of the 1200A, this will not only delete the array, but also delete any partition information along with all of the data on all drives. Once the delete option has been chosen there is no way to get the data back.