QtCreator: No valid kits found

Though OP is asking about Windows, this error also occurs on Ubuntu Linux and Google lists this result first when you search for the error"QtCreator: No valid kits found".

On Ubuntu this is solved by running:

For Qt5:

sudo apt-get install qt5-default

For Qt4:

sudo apt-get install qt4-dev-tools libqt4-dev libqt4-core libqt4-gui

This question is answered here and here, though those entries are less SEO-friendly...

Found the issue. Qt Creator wants you to use a compiler listed under one of their Qt libraries. Use the Maintenance Tool to install this.

To do so:

Go to Tools -> Options.... Select Build & Run on left. Open Kits tab. You should have Manual -> Desktop (default) line in list. Choose it. Now select something like Qt 5.5.1 in PATH (qt5) in Qt version combobox and click Apply button. From now you should be able to create, build and run empty Qt project.