cannot remove or write zeros to backup drive

On my computer I have my main hard drive (WD 500 GB) which is drive C:\ with windows 10 preview.  I also have a backup disk installed.  Today I added another hard disk with the intention of making the backup disk and the new disk dynamic.  After installing the new disk, I went to disk management and (supposedly) did this.  Windows disk management said that I had successfully created dynamic disks, however, the the computer still saw two separate disks.  
Now, I went back to disk management and changed the new disk back to basic disk, but it would not let me on the backup disk.  attempting to delete the volume on the backup disk would not work either.  

I went to MiniTool partition magic and attempted to write zeros to the back up disk and partition magic warned me that if I did this, I would not be able to restart my computer

Then I found out that if I unplugged the backup disk I cannot boot my computer, even if I go into bios and made sure that the preferred boot disk is the 500 gb hard disk.  Can someone explain to me why this is and what I did wrong when attempting to create dynamic disk?
Will Schmidtowner Asked:
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The boot/Mbr was on that drive.
Double check the disk order in bios.
You would need to use your windows disk to recreate the boot
Bcdedit bootrec after you make sure the 500GB drive is the first drive sata connection.
Gary CaseRetiredCommented:
Step #1:   DISCONNECT the disks you do NOT want to use for booting;  then boot to the Windows 10 installation media and do a boot repair so the disk will boot with no other drives installed.

THEN you'll be able to reconnect your other drives and reset them as you want.

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Will Schmidtowner Author Commented:
Thanks for you help.  I will do this in the morning and get back with you.
Will Schmidtowner Author Commented:
Sorry I did not get back to you sooner.  I opted to follow Garycase and that worked fine. I am sure that Arnold's suggestion would have worked fine also.  thanks for your help on this issue.
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