How to get Windows back to default state

[bwmodular]

I've managed to mess up the Window/Tab layout of my toolbox and I've been trying for ages to get it back to how it was, but no matter what I try it's not working. The best I've managed to do is get the different windows docked with the tabs at the bottom of the screen like this:

but I can't get them back to the OOB configuration. I've tried so many different layouts, but I can't get it back to how it was before.
I'm almost embarassed to ask such a simple question, but maybe it'll help someone else out too.
Is there a way to revert to the OOB windows layout?