If you want to bring up the standard Windows 'About..' dialog box, then you can use ShellAbout() from the ShellAPI unit and customize the appearance by adding your own text, application name and an icon.
The downside to this technique is that it will say '(c) Microsoft' in the box.
The upside is that you see the registered user and some system parameters (free space..). It's a quick-and-dirty solution for an About-box.
uses
Windows, ShellAPI;
procedure TForm1.About1Click(Sender: TObject);
begin
ShellAbout(Application.MainForm.Handle,
'Address Book Application',
'Version 1.23.3beta'#13#10+
'Compiled 2001-08-03 15:25:10',
Application.Icon.Handle);
end;