CopyFile/fi

// flags for copy
type
 TCopyFileFlag = (
   cffOverwriteFile,
   cffCreateDestDirectory,
   cffPreserveTime
   );
 TCopyFileFlags = set of TCopyFileFlag;

function CopyFile(const SrcFilename, DestFilename: string): boolean;
function CopyFile(const SrcFilename, DestFilename: string; PreserveTime: boolean): boolean;
function CopyFile(const SrcFilename, DestFilename: string; Flags: TCopyFileFlags=[cffOverwriteFile]): boolean;

uses 
...
fileutil
...
CopyFile('c:\autoexec.bat','c:\windows\temp\autoexec.bat.backup');

procedure TForm1.Button1Click(Sender: TObject);
var
  ok:boolean;
begin
  ok := false;
  if OpenDialog1.Execute then
    if SaveDialog1.Execute then
      ok := CopyFile(OpenDialog1.FileName, SaveDialog1.FileName);
  if ok then MessageDlg('File '+OpenDialog1.FileName+' successfully copied to '+
      SaveDialog1.FileName,mtInformation,[mbOk],0)
  else MessageDlg('Copying failed',mtWarning,[mbOk],0);
end;