Questions on setting up a RAID1 array on an existing system

Your process would be right if you were converting a data-storage-only unit into a RAID1 array. But you've missed an important item for your situation, I think - I presume you are booting from the current single drive, and want to boot from the RAID1 array. The Windows you have installed already does not know how to communicate with a RAID array. Even if you install a RAID driver in it now, that only gives it the ability to load that driver from the hard drive AFTER it has already booted. That does NOT allow it to BOOT from the RAID1 array.

As I understand, there are two basic ways around this. The straightforward way is to get all your data and app software backed up to a drive (or, in your case, remove the existing drive and mount it in an external enclosure you can use later as a backup unit), then install only the pair of new drives in your machine. Then you create the RAID1 array. Then you do a complete fresh install of Windows to this array, including installing very early (through the F6 option) the RAID drivers that become a permanent part of this particular Windows install so it always can use the RAID array. After that's done, basically you need to re-install all your application software, configure them, then copy all your data files from the backup unit (the old drive mounted in the external enclosure) to the new drive (RAID1 array).

I don't know if there is any way to do this job more simply, without re-installing all your app software.

The other option I know of amounts to establishing on ONE of the new drives a small Partition to which you clone only the Windows OS portion of your old drive. This becomes your non-RAID C: drive to boot from. Then you create your new RAID1 array from the remainder of that drive (and it will use a chunk of the second drive of matching size), and this will be a data storage only drive. Then you could copy all your old stuff from old drive to new RIAD1 array. But that still leaves you a lot of work to get the transplanted Windows on the new C: drive to recognize and use all its old applications that have suddenly been moved (with their config and data files) to a different drive.

In general when buying a pair of drives for RAID use, get them as identical as possible so all their performance parameters match. Buying two drives from the same manufacturing batch does NOT usually mean the probability of failure is higher. Most failure causes are NOT a repeatable systematic fault in the production line, but rather are from random fluctuations that affect only a very few units in the day's or week's batch. In fact, your odds of getting two exceptionally good units are at least as good as the odds of a pair of bad ones.