We have a Lenovo All-in-One Desktop running WIN 10 that won't boot up following an automatic update. Just one day previous, the HP desktop (also WIN 10) did the same thing and was resolved by performing a System Restore. When we ATTEMPTED a System Restore on the Lenovo it says it can't do it because the drive is not protected and we need to enable system protection.
This has to be done from the command prompt because Windows will no boot. Would SOMEONE please tell me the exact steps and correct syntax needed to accomplish this?   So the HP Desktop is now running pre-patch and is subject to crashing again with problem or it was able to successfully get through the update the 2nd time around?

Do you have the system recovery media for the lenovo to perform a repair installation? 

Did you play around with or install/configure BitLocker on this system prior to this issue?Thank you for your reply. I am using the HP now. Was afraid to turn it off because of the updates,  but we had a power outage two nights ago and it powered back up with no problems. My husband tried the "back up/recovery" DISCS he had made for the Lenovo - they were made before he updated from WIN 8.1, though so we thought that may be why it didn't work. I am not sure if he had Bitlocker or not, but I know that years ago (previous WIN XP  computer) he used Bit TORRENT a lot. A few MONTHS ago he was streaming some movies again and I am not sure which one he used, but he removed it altogether in January. He is on the road right now and I will ask him when he calls me which one it was.  Should we start shopping for a new PC, in your opinion? It would be awesome if there is a chance of saving his because I was planning to replace this HP to start fresh when I begin to work-at-home.
Is it possible to put his hard drive into this PC? This is not an all-in-one - I have a tower or case or whatever it is called these days. I am 53 and he is 59 and we used to be pretty tech-savvy until took off faster than we could keep up. Thank you for any advice.