Having had this error and spending a long time searching for an answer to how to copy a file into a folder that kept giving me this error despite following the online advice for making myself the owner of the folder (which seemed to do nothing) the way that worked for me was simple: move the file into the folder.

By that I mean open two explorer windows next to each other, one with the source directory, the other with the target directory and simple drag the files/folders from the source to the target.

Seemed to work for me when all else failed (mind you, up to them I did toggle UAC back on — some have said switching it on or off, basically reverse what you have — and I also made myself the owner with Full Control of the folder, these may also have played a part).