Recusive GetFiles for DirectoryInfo via a C# Iterator

I have been working on a project using C# Express and so I have been playing around with some of the new C# 2.0 features. In my project I had a need to get all the files of a particular type in a given directory including all sub-directories. The DirectoryInfo class has a method GetFiles that takes a search pattern (ie "*.exe") but it only searches that directory it doesn't search sub-directories. So I figured this would be a good chance for me to play with these new things called iterators. At any rate I wrote a recursive version of GetFiles using an iterator so that I could do a simple foreach loop to get all the files recursively.