It's not ALWAYS a message about your screen resolution being too low, I get it occasionally and I NEVER change resolution on my screen, it remains at 1280960. Usually that error message pops up (at least at my computer) if I have had to shut down Poser with the three finger salute. But so far the only occurrence of No Window has been if I've opened other programs while Poser was loading. It doesn't like that. However, a simple click on "new" loads a nice empty) document --- *) Empty because I've set it to load an empty one in my preferred State. Another thing is.. you don't need to move anything in your Runtime. Even if you have to reinstall, the "old" stuff stays there, if you've installed new content. Existing files are overwritten of course, but nothing is deleted unless you do so manually. I'm not sure what happens if you uninstall Poser, but just reinstalling on top of the old leaves your Runtime in place

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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.