If you are using Visual Studio and opened an existing or created a new Windows Phone 7 project you may get the following build error.
Zune software is not installed. Install the latest version of Zune software
The reason it is complaining about the Zune software is that it is assuming that you want to deploy to a Windows Phone 7 DEVICE and NOT to the Windows Phone 7 EMULATOR. IF you are deploying to a REAL Windows Phone 7 DEVICE then you should install the Zune software. More likely, you want to test your project in the Windows Phone 7 EMULATOR that works with Visual Studio 2010. To target the Emulator, you just need to the target in your Drop Down List from Windows Phone 7 Device to Windows Phone 7 Emulator. After making the change, try debugging again and it should work much better.