The redistributable with .NET 3.5 contains .NET2.0, .NET 3.0 SP1 AND 3.5 That's why it's big. BTW it says, that it needs to download something from the Internet, which is not actually truth, as it can be installed without an Internet connection. But it DOESN'T contain .NET 1, which you have to download and install separately. Refer to this thread.