From repair boot mode, select troubleshoot, advanced repair start up and select option 4 to boot into Safe Mode.  From there, just do a reboot and your system should boot as normal again. Otherwise, remove the new drive and change your SATA operation from RAID to AHCI following the process below.  Then adding the new drive back.   Run elevated cmd as administrator  Copy and paste or type this command, which will start Windows in Safe Mode the next time you reboot: Reboot the computer and enter BIOS setup. Change the SATA operation mode from RAID to AHCI. Save changes and exit Setup and Windows will automatically boot to Safe Mode. Click on Start and type cmd and select run as administrator, as in step 1. Copy and paste or type this command, which will start Windows in Normal Mode the next time you reboot: Reboot and Windows will automatically start with AHCI drivers enabled.  
I have a 9020 with 32GB and 1TB HD. I added a Seagate 2TB 7200 HD to the system as a data drive expecting it to find it and boot up okay. I've not been able to reboot into my original drive though it worked great yesterday before adding the HD. I did do this first, and also tried going to ATA:  [URL] The 9020 went into repair mode but could never repair itself. The Windows 10 is an enterprise version. I'm not sure what else to try without having to reinstall the OS and software on it. Most of the time, I've added another HD, Windows found it and I could reformat or access the drive after adding.  I really don't want to have to reinstall Windows 10.        
Can't boot to Windows 10 on Dell 9020 after adding a 2TB HD