I was trying to follow this guide to rename my file system in Windows which I have used in the past once before. When I tried to rename my User folder via the command prompt (in administrator mode) I received an "access denied" message. To get around this I tried to open the advanced security settings for the User folder in explorer and tried to change the ownership of it directly which produced the error message in the title. What was more worrying was that I randomnly decided to try and go to the user accounts section in the control panel and tried to click the 'Add or remove user accounts' option however nothing is happening when I click it. I am not sure whether this is related.
UPDATE: I reversed step 4 in this guide and now I can reaccess control panel and I am not getting the error. Still unsure how to proceed though.