Visual Studio 2008 - re-prompt to migrate web app from .NET 2.0 to .NET 3.5

If you have already been prompted to migrate your solution from .NET 2.0 to .NET 3.5 and you responded "No" at the 开发者_Go百科time, how do you get Visual Studio 2008 to re-prompt you with this question?

Sorry, if there is a real simple solution to this one.

I don't think there is a way to get VS to do it for you. You can go to each project in your solution and set the 'Target Framework' on the 'Application' page of project properties.