Problems copy file from CD using Block Read - Access Denied

I have written an install program, which gets a destination path from a user and then copies a database (mdb) file from a CD to the destination.

The install program works when I test it from the hard disk, but when I burnt it to a CD and went to test it, the database file was not copied.

I put some dialogs to show me what was happening, and I get an error msg re: Access Denied

Code below

=====================
var
  FromF, ToF : file of byte;
  Buffer : array[ 0..4096 ] of char;
  NumRead : integer;
  FileLength : longint;

begin
  try
   AssignFile( FromF, Source );
   filemode := fmOpenReadWrite;
   Reset( FromF );
   AssignFile( ToF, Destination);
   Rewrite( ToF );
   FileLength := FileSize( FromF );

      while FileLength > 0 do begin
        BlockRead( FromF, Buffer[ 0 ], SizeOf( Buffer ), NumRead );
        FileLength := FileLength - NumRead;
        BlockWrite( ToF, Buffer[ 0 ], NumRead );
        Position := Position + NumRead;
      end;
 
   CloseFile( FromF );
   CloseFile( ToF );
  except
        on e: Exception do
              MessageDlg('Error :'+e.Message, mtError, [mbOK], 0);
  end;  // try/except
end;