I know this is a nit-noid question, but ...
While converting a VS 2005 (.NET 2.0) project to a VS 2010 (.NET 4.0 project), I encountered a dialog stating that the project was written in a previous version of .NET and did I want to convert the project to the newest version of the framework. In addition, there was a check box that prompted me to do this automatically each time I convert a project. I accidentally left that checked when I didn't want to. Does anyone know where that option is set in the options of VS 2010.