Closed Issue: Demo Samples not Working??? [11]

I am not sure what I am doing wrong. I just downloaded the demo sample for Windows Phone 7.
I have Visual Studio 2010 Express Edition for Windows Phone 4.0.30319 SP1, XNA GameStudio 4.0 and also I have the latest Windows Phone 7 Developer Tools with Mango Update.
I get an error alert upon debugging saying "The application failed to start debugging. Please verify whether the application is installed on the target device."