I am using Windows 7 and Visual Studio Express 2013. I have installed Windows Phone 7.1 SDK and Windows Phone 8.1 SDK. When i go to VS menu under DEBUG->Other Debug Targets->Debug Windows phone internet Explorer nothing appear under Target Device Dropdown list in order to choose emulator. Any ideas how to configure them?.
The Windows Phone 8.0 SDK include the ability to create apps for 7.1 and 8.0 so there should be no need to install the 7.1 SDK.
Developing apps for 7.x is not supported in Visual Studio 2013. If you must target 7.x devices you'll need to use VS2010 or VS2012.
If you want o build for Windows Phone 7.x you should use Visual Studio 2012. You can install this AND Visual Studio 2013 on the same machine.
Again one more thing is you can not build Windows Phone 8.1 apps on Windows 7 OS. So it is advisable to install windows 8.1 / 10 OS and install both VS2012 and VS2013.