Visual Studio opens multiple windows


I got a new computer with a fresh windows 7 professional installation.

I have installed Visual Studio 2013 Community edition.

However when I double click a C++ source file in the Unreal Editor it opens up Visual Studio twice,
one windows contains the project with zero tabs and another window pops up with the files I double clicked on in the editor.

Does someone else experience this problem? Is there a new setting to change this behaviour?

Thank you for your help