Right-click the file/program, click "Copy", right-click where you want the duplicated file/program to go, and click "Paste". ------ Or to duplicate a program you can use Installrite...
In DOS copy source destination In Linux cp source destination Destination defaults to the current directory when different from the source. The syntax varies from one operating system to another.
If you are referring to those that appear in "My Documents" and again within the "C:" directory, these are "mirror" files ... listed twice for convenience sake, but there are not two identical files...