If you use a computer long enough it will crash. By crash I mean crash hard and it won’t recover itself on its own. The hard drive may fail or some other component. You can try bringing it in to a repair shop and wait a week or two then get a bill only to have the computer returned to you with everything wiped off it.
You need recover the OS with the proper license. You need to get it fast. I recommend taking a snapshot image of the entire drive so that you can restore it quickly yourself. It takes a little reading to follow instructions, maybe 30-60 mins.
You will need a tool to make this quick and easy and I recommend DriveImage XML. There are many others so choose your favorite but don’t overpay.
I always have a few SD cards lying around or a spare USB thumb drive and you can make use of these on almost any computer. So prepare, the day is coming.