The .NET framework is Microsoft's take on Java - a single VM for multiple plaftorms (essentially multiple versions of Windows, until Mono came along) that can be targeted by several different language environments.
Damn impressive piece of engineering, and slightly better (architecturally) than Java. Microsoft has to deal with the very impressive Mono cloning effort, though - which is both competition and a boost to .NET, since savvy companies are doing more and more dual-VM development.