This all depends upon the data and space on your computer.
As others mention, you must run the command-line as administrator, else you will get an insufficient rights error message on the net stop command.
Once you've downloaded the iso, just burn it on an USB drive or something else using whatever you want (like rufus).
Windows 10 stuck at 99 percent reset is a common problem reported by several Windows 10 users almost daily.
I just upgraded from 8 to 8.1 and immediately tried upgrading to windows 10. I'm going to list everything I did but my suspicion is the most important thing I did was frequent disk cleanups.
I got this same error so I killed the process and retried and restarted my computer a few times. *side note - it won't let me close it unless i end process from task manager. Instead of trying to straight update to windows 10 I updated 8.1 as much as it would let me.