Moving operating system from SATA mode to RAID 1

Switch to raid mode, and during boot up press the key combo to go into the raid bios (ctrl-H ?) then add the boot drive as a single drive. Exactly how to do this varies with the chipset so if its not obvious let us know exactly which motherbd you have.

Theres no need to reinstall as AHCI is a subset of raid and the drivers will work with the controller set in raid mode but this doesnt mean you can skip running a backup on your important data. Important data always need to be kept on multiple drives/disks/tapes (you get the idea)

Okay hold up. If you enabled in BIOS AFTER OS install, that was the first mistake. You should have changed the registry hack first then reboot and change the BIOS to RAID. Windows would then pick up the change after the face but you didn't want to go right to RAID 1. See http://www.gregledet.net/?p=569 for example, as multple articles are available if you google Windows RAID regedit .

Now that would put in RAID 0 with a single drive (you didn't say how many drives you have). If your unfamiliar with the combinations look here (http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/) for a visual representation to see how the data gets set up. Personally unless you have at least four drives (http://www.pcmag.com/article2/0,2817,2370235,00.asp RAID 4) so three drives are used with one drive for parity (stating what is stored across the three drives) so if one fails you can hot swap it out on the fly, there is no need for RAID use in a personal computer, and this is from personal experiance.

If you go RAID 1, where both drives mirror each other (you need two drives) then it will affect performance as your computer is constantly doing twice the reads and writes, to ensure the data is constantly read/written correctly.

If your looking for performance gain, your real only solution is to reinstall OS to a SSD as drive one, then everything else to HDD drive two for storage and programs.

when you set the controller mode to raid in the bios you set the sata ports to raid mode. Now instead of passing the drive thru 'bare' the raid controller basically acts as a middle man (to manage the raids) Now he wants all drives on his controller to be raid drives. Some controller are smart enough to know you dont raid cd/dvd/br drives and pass them right on thru but when he sees hdds or ssd's hes waiting for you to tell him their role. You need to go into the raid bios and tell him the SSD is to be a single drive. Some controllers have this "Single Drive" setting while others need you to setup the drive as a 1 drive raid0, 1 drive raid1, or 1 drive JBoD.

your choice are 3
1: to configure the ssd as a single drive

or 2: move SSD to a sata port that not being used as part of the raid controller. Either you need to read your manual or we way need to know which motherbd you have so we can read it for you.

or 3: revert the bios back to ahci mode, boot up and when windows is done loading go into drive manager and use windows to create a mirror (instead of your chipset raid) of the two drives.
http://www.howtogeek.com/howto/17926/use-drive-mirroring-for-instant-backup-in-windows-7/

Because RAID is a accomplishment both of hardware AND software for all the drives collectively, the OS can not sit outside of the RAID and talk to it through some translation, it has to be INSIDE the RAID to talk to everything there.

It might be best to think of RAID as a Bank Vault, there is either two ways it works, either with the door closed and everything is secure and locked away (but you have to be INSIDE the vault to touch anything) or open for anything to access it from anywhere since the 'door' is open.

I provided two links that discuss what RAID is, how it works, and the different statuses. The problem at this point is you will need to 'break' the RAID (wiping both 2TB clean) and have to start over. There is no way to access the RAID 'externally' from the NON-Raid drives, and the RAID is preventing OS from loading because it isn't 'inside' the RAID to access the RAID, which the hardware says needs to be running to access any drives at this point. If you included the 1TBs in the RAID, you would immediately lose 1TB on both the 2TBs, as it has to be apportioned to the lowest standard, and potentially any data0.

I still was trying to understand the purpose of your RAID. Your apparently trying to have a constant backup running of your 2TB to ensure no loss of data (main purpose of RAID 1)???? Realistically this isn't feasible unless you have the drives in Hot-Swap Bays in a Server Case / Rack??? Then at point of failure you slide out one or the other drive, put in a replacement exact same model 2TB and the RAID fixes itself (supposedly) by replicating to the new drive the same info as the 2TB (in RAID 1 it is a common known Gamble for that, as likely to be 'broken' with all data loss as well as proper work as hoped for).

In actual practice you would need to shut down and be offline till you bought another 2TB of the same exact model, maker, type, etc. Open the case, then swap them out (broken one for new one), then wait at least a couple of days for it to replicate that much (2TB) of data. Even if you actually had only 500GB of data on it, it still has to replicate 2TB exactly to synch the drives into RAID 1. Hence why RAID 3 is minimal for such designs, and RAID 5 is the baseline standard for ALWAYS (100% uptime) online and validated data (like websites or your email account).

IMHO I would just suggest the 2TBs as OS/Programs and a Data drive (downloads, etc.) then use the 1TB with backup software that compresses, and do a backup, then scheduled (in background) incremental backups (only backup stuff that changed) of your OS/Programs 2TB. Normally the meantime of failure for a drive is about the time when replaced (3 years for business class, 5 years for consumer class systems). So normally people worry 'Windows' will get broken and have to reload everything all over again, so the backup of just that portion will provide that failsafe.

Hope this help.

In replay to Tom
1) I think you are thinking of raid 0. Raid 1 will indeed maintain uptime should 1 drive fail. It will even remain bootable.
3) not quite right here, Its journaled not encrypted. Journaling means the OS knows who the onwer is and will block access to others. To gain access to anothers folder is a piece of cake; theres zero encryption involved.
4) never say never. There are situations where the risk associated with encrypting raids is worth the risk.