Hi,
I just recently encountered the same (0x80041321) problem along with getting the same corrupt "Task Scheduler-Corrupted Task Image" message and the same "Command Prompt-Access Denied" message.
I was able to overcome the "Command Prompt-Access Denied" issue by going around 3 pages deep into the replies on this web site and following the instruction in the reply from "SuzanneK sent in on September 03, 2015".
Just remember to press the Return button after entering each of the three individual lines of information.
After completing all 4 of her instruction points I logged out and restarted my PC then plugged my External HD back in and was able to do my back up.