The error message is pretty explicit:
The requested operation cannot be performed on a file with a user-mapped section open
The file is open, probably elsewhere in your own app - and cannot be opened by the external process to copy the file until it is closed.
Check all your other code and make sure you do not maintain any access to the file. That includes any Image controls you have loaded from the file, and so on.
As a good practice, use a
Using
block around any streams etc. throughout your code to ensure that the file is correctly closed and relevant structures disposed when you are finished with them.