Just by looking at them, Type II fixes appear to be made with IExpress and a custom INF to do the install work. Technically, Type I fixes require a specific program (see the Hotstream forum for more info), but the few that have it don't want to share because they promised gurgelmeyer they wouldn't (as if that really matters anymore ). Depending on what you're aiming to do, you can simulate a Type I fix with a 7zip SFX installer, though. I've done that with my .NET 3.0 installer. Catch me on IM and we can discuss it more.