Installing on top of an existing installation won't harm already installed content. Not on Windows at least. So that ought to be safe.

Runtime Repair sounds like a good solution though - if it works on a Mac...

FREEBIES! | My Gallery | My Store | My FB | Tumblr |
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.