By chance I've discovered that my Win 10 has defaulted to encrypting my main HDD (i.e. the C:\ Drive), with bit-locker.
If you are not aware of this, & then subsequently have Win 10 fail to start, I think that you will find that you can kiss your Data goodbye (since you won't have the Bit-Locker Key!).
However, I've discovered that (under "Settings", "System", "About") you can switch it of and/or obtain a Recovery Key.