At the bottom of your (now in 4 parts) window, to the left, there's a little square icon with a drop-down arrow beside it. Click that and select the one that is just one square and you're back to normal :o)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.