Hey!!
I faced the similar problem few days before. Here's what worked for me.
As the error message tells that it was unable to modify a necessary file maybe O.S blocked it. Here's what I did::
1. Uninstalled origin completely... Meaning deleting the temp files and a fresh reboot..
2. Go to Origin.com and sign in there..
3. Download origin
4. Before installing it, disable all your anti malware including Windows Defender(inc. public private domain etc.)
5. Then run it as an administrator
6. And everything went fine
P.S :: I also faced a issue where the pop up origin login screen showed it was currently offline and you must be online at first login. This steps solved that too..
I hope those steps works out for you too. If it does or doesn't please let me know...
Peace Out...
