I just shot a short video giving a short demo of Moles, a new framework that allows replacing any .NET method with a delegate. In the context of unit testing, one can use Moles to isolate from environment dependencies (such as time, file system, database, etc...) even when those dependencies are hard-coded through static method or sealed types. In this demo, I go through the famous Y2K bug and how to test it...

http://channel9.msdn.com/posts/Peli/Moles-Replace-any-NET-method-with-a-delegate/

Moles is part of Pex: http://research.microsoft.com/en-us/projects/pex/