First, get Windows booted-up. Then you'll need Visual Studio Express, and MSDN. Keep in mind that .NET will be very different than PHP. If you'd like to gain a bit more familiarity with .NET's way of working, while using PHP, you could examine a framework like Prado which acts like a hybrid.
Out-of-the-box PHP isn't Object Oriented. .NET is. I remember my first week learning .NET I was very frustrated because I couldn't include() a sidebar navigation. I had to learn that controls were objects, and objects had to be created and added to other objects. It's a much better way of working (which is why many PHP developers adhere to OO-Frameworks like Kohana) as you'll eventually see.
.NET also comes in two primary languages: C# and VB.NET. If I were you, I'd stick with C# as the syntax will be most familiar coming from a PHP background - VB.NET is much more verbose, and doesn't make use of curly-braces and semicolons.
As with all programmer endeavors, keep StackOverflow bookmarked, and make heavy use of it when necessary. It will likely be your most valuable resource in learning any new programming language, or framework.
Best of luck!