If you open a Excel file using the OPEN AS COPY option, then a new file is created and saved in the same directory of the original file. So if you have a file, say test.xls in D drive. Then if you open the file as copy, then Excel creates a file in the D drive with the name Copy(1) of test.xls.

You can access this file through the path D:/Copy(1) of test.xls. You can always rename and copy your file somewhere else but by default Excel saves the copy of the file in the same drive. Also, Excel duplicates the original file and whatever is in the original file, it is copied including formats, formulas and other functionalities.