A few weeks age I repaired a PC which had been originally purchased as a Windows 7 PC but was subsequently upgraded to Windows 8 then 8.1 and finally to Windows 10. This PC had ended up in a state where the operating system was unable to write to it’s own hard drive, so there was no possibility of any more Windows updates working.
This whole repair really highlighted the importance of keeping a record of all your software licence agreements to make everything much simpler in the event of an issue such as this. We are probably all guilty of not keeping this information safe and assuming it will be OK, but it really can be costly if you lose your Office licence key, or Adobe Photoshop licence key for example.
Just a thought, and of course we need these in paper copies in the event of not being able to access the hard-drive !!
Hope this helps