Quick question, hopefully. My wife has a late 2013 iMac 21.5". I replaced the HDD with a Samsung 850 SSD last weekend. I cloned the original drive, which I still have. She ran the software update today and we are getting this error now. Anyway, if I put the original hard drive in a USB 3.0 enclosure and boot from it, would I be able to access the data on the SSD (internal) as if it were an external drive? She's spent all morning editing a wedding and was about 400+ photos in when the update crashed the iMac. We don't use time machine as a backup, so this could feasibly be lost if I am unable to access the date on the SSD. I am pretty sure the drive is fine, but we are just stuck in the loop as the system is trying to finish the upgrade. I could also open the iMac back up and take the SSD out and put the original HDD back in, but it would be much faster and easier if I could just boot from USB and still access the SSD. Thoughts?