When copying a file over an existing file, the existing one was in use by another application.
I then accidentally clicked on 'Schedule' instead of cancel.
How to delete a scheduled task.
I went over om to Task Scheduler, assuming it would be there, but regretfully could not find anything in the Task Scheduler library relating to the above task.
Scheduled copies happen on reboot.
The list of things to copy is stored in the registry, and processed very early during Windows boot-up: Use PendingFileRenameOperations Registry to Automatically Delete or Move a File On Reboot | Q's Tech Babble
(If it was done through Task Scheduler, the file could already be in use by the time the task ran.)
I don't know where the task is stored (as said I accidently clicked on schedule, instead of abort)
Hoping I would find anything in the task scheduler as outlined on TenForums
and simply delete it. Doesn't seem to work that way, there is more to it, so I let it rest.
Peforming the task will fail anyway: copying a file from an unmounted encrypted drive to an external USB drive that isn't available either.