Holodeck is a software fragility and security testing tool that allows you to analyze the interaction of the application with its environment, and force it to manage error conditions that may lead to failure or breach. It is a filemon, regmon, netmon, processmon, libmon, and apimon all in one user interface, so you can scope by process or process and thread. This allows you to understand your application better than you could otherwise because it can very hard to see all the dependencies and interaction.
For security testing, Holodeck exposes your applications attack surface, and using sophisticated fuzzing and blocking techniques, allows you to analyze and lock down areas in where your application is vulnerable to exploit. Version 2.8 includes support for Windows Vista and .NET Framework 3.5.