Tomasz Janczuk of Microsoft posted about owin, .NET and node.js. Here is the project on github. The owin project allows hosting .NET 4.5 code in node.js applications running on Windows. You need Windows x64 with node.js 0.8.x x64 installed (the module had been developed against node.js 0.8.19). You also need .NET Framework 4.5 on the machine.