If you started the task from the context menu, and it completed normally, there will be no task entry in the schedule. If the Task list has been cleared because of an error, there should have been some sort of error dialog.
Are there any folder names in the root of the target drive that you don't actually recognise?
Another possibility is a pre-existing issue with the file system before you ran Eraser. Could you run check disk on the target drive? As it's the system drive, Windows will probably ask to do the check on reboot.
David