Of course, to use the Python solution, you would have to have either Poer 4 Pro or Poser 5, as Python doesn't work in plain old Poser 4.03. But there are loads of useable python scripts (in free stuff) to delete lights, change them or do all sorts of nifty things with them. And yes, deleting existing lights before adding a new lightset is a good idea in general.

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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.