Uknown Startup entry

Thank you for the detailed explanation.

Because Onedrive doesn't want it there, it deletes the folder at boot, but ONCE... That's why is under the Run Once key. If it was to be recreated by Onedrive it would have been under the 'Run' key, since the app does not want it.

My understanding is that after an upgrade of Onedrive, the installation process created the Registry entry for cleanup reasons. In the following boot it deleted the folder, but for uknown reasons kept the entry. Error? Maybe!

Either way, I exported and kept the Registry entry, just for precaution, before deleting it!

When you upgrade to 10 (or clean install) after logging on first time OneDrive is always updated. Same happens if you make a new user and it doesn't matter whether you use OneDrive or not (if you make a new user and sign on you'll see a "Updating OneDrive" notification).

That key is to delete the old version and it has worked (or didn't need doing) as you don't have the directory it is trying to delete.

Because it is in RunOnce the key should have done what it wanted to do and then have been deleted the first time you rebooted. There are some situations where a RunOnce key will not be deleted - if it has a ! sign in it (which it doesn't) and the command failed, if your user is not an administrator... RunOnce Registry Key - Windows 10 hardware dev

Anyway, it has done what it wanted to do (delete the old directory), or what it wanted to do doesn't need doing, so deleting it is no problem at all.

The '17.3.6281.1202' folder is the one I have too. It's the updated one.
The RunOnce reg-key deletes folder '17.3.5892.0626' which apparently is the updated OneDrive version.

I believe that lx07 has put it very well, regarding what OneDrive does.
The RunOnce command did what was supposed to do. Deleted the old folder '17.3.5892.0626'.
The problem is why after completion, the RunOnce reg-key was not deleted from the Registry, since my account is Administrator.
So I tend to believe that is probably a bug from the OneDrive update process.

Dude also had the problem with the RunOnce reg-entry.
(Solved Uknown Startup entry - Windows 10 Forums)

I backed up the RunOnce reg-key and deleted it. No problems so, far.