The DeleteFile() procedure is declared both in the SysUtils unit and the Windows unit. The following example demonstrates calling both procedures. The version declared in the SysUtils unit accepts strings, and the Windows version accepts PChars.

procedure TForm .Button Click(Sender: TObject);
var
  s : string;
  a : array[0..MAX_PATH -  ] of char;
begin
  s := 'C:\SomeFile';
  SysUtils.DeleteFile(s);
  a := 'C:\SomeFile';
  Windows.DeleteFile(@a);
end;