Eh? No, Microsoft .NET is a complete runtime environment, just like Java.
[start technobabble]
For example, normal programs would run in native mode, i.e. directly in the operating system, .NET programs run in the intermediate .NET environment, and that environment runs in the operating system. So think of it as a mini platform on top of Windows, that is simpler to program for, and hence allows a simpler, faster, and cheaper development process.
[End technobabble]
Microsoft .NET is needed for the toolset, I can't think of other components that would need it.