uses
ComObj, ActiveX;
function CreateGuid: string;
var
ID: TGUID;
begin
Result := '';
if CoCreateGuid(ID) = S_OK then
Result := GUIDToString(ID);
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
Edit1.Text := CreateGuid;
// or: Edit1.Text := CreateClassID
end;