Resource file and Localization

Question

I am trying out localization in C# 3.5. from what I learned, I can have seperate resource file "*.resx" for each local i want my application to support and at the same time one default resource file in case no specific resource is available. so in my test application, i have 2 resource files, resource1.resx and resource1.en-AU.resx. In my PC regional setting, i set my country to Autralia and format to English Australia, so I assume my local is Autralia that's why I create the second resource file. The problem is when I run the application, it picks up resource from the default resource file not the Australia one. So can you tell me what's wrong? It suppose to pick up resource from the second resource file which is "resource1.en-AU.resx". And when I change from "resource1.en-AU.resx" to "resource1.en-US.resx", only then the application picks up resource from the second resource file. Thanks for your help.