Copy is used when we operate on the U disk file, paste the way, if the copy is the file on the U disk, then this file will appear in the Clipboard, in a pending state, in this case, delete the U disk will pop-up can not stop the U disk prompts.
So you need to clear the clipboard before removing the U disk, or paste it somewhere on the disk.
First open Task Manager, click on the Process tab, find the process named Rundll32.exe, put it to the end, if pop-up to close this process prompts, click Yes, close this process and then try to delete U disk again.
This method also needs to use Task Manager, locate and close the Explorer.exe process in Task Manager, and then click on the file in Task Manager to re-establish a process called Explorer.exe.
If the above method does not solve the problem, we can choose to unregister the computer to solve the U disk can not remove the problem.