After many reboots, reading manuals and posts, trying many methods with no avail, I finally figured out the problem.  As it turned out, I had no chance of getting it to work the way it was.  The fix, and the ONLY thing that made the difference, bar none, was updating the BIOS to the latest, 08.  After that EVERYTHING worked EXACTLY as advertised.
How can get it to mirror the current information from the first partition of drive 0, the C: system drive, to the first partition of drive 1?I got an emergency call in from someone with a Dell PowerVault 725N, which I know nothing about.  From what I read, it was set up as a typically as a two RAID-1s, one for OS C:, one for factory OS D:, and a big RAID-5 across all 4 disks E:.  It lost a disk.  However, when it lost a disk, the RAID-5 no longer worked with the one drive bad.  Obviously that shouldn't have happened, but it did.  I gathered that the drive was hanging the bus sometimes because sometimes the OS wouldn't freeze also.  The fix was to remove the bad drive, which I did, and copy off the data, much to their relief.  The found a new drive in town for it, and I put it in.  This is where the problems started.- When I put in the new drive, it came up fine, I wrote the signature to the disk, and set it up dynamic.- The RAID-5 E: replicated to the disk fine, but not the mirror of the C:  I could not get it to mirror, so I broke the mirror, and deleted the "missing disk"  It only holds 4 disks, and all 4 are there.- When I try to mirror C: to the free space on the new drive, it returns the error:  "Could not allocate contiguous space or partition." before I can even select the modify button.  - I deleted the E: volume, RAID-5 volume, to get all of the space back on the new drive.  Therefore, I have a drive 0, with the OS on it in the first partition, a drive 1 with nothing on, and set up dynamic, and drive D: which is mirrored to the first partition of disk 2 & 3.  - Again, when I highlight drive C:, and select Add Mirror, I still get the error:  "Could not allocate contiguous space or partition."  Obviously there is a massive amount of space on drive 1 to mirror to.- Dell pulled all of the docs that people were using to fix this problem.  How can get it to mirror the current information from the first partition of drive 0, the C: system drive, to the first partition of drive 1?Thanks!
PowerVault 725N RAID: How can I mirror my C: partition from Disk 0 to Disk 1?