I had this same problem and got excellent answers on this thread. http://www.renderosity.com/messages.ez?Form.ShowMessage=1057911... I downloaded the delete all lights python script in free stuff which has been updated for P5. It works just great. Now everytime I try new lights I first delete the old ones with the script. All of my favorite P4 lights that I purchased and those from free stuff work great in P5. Hope this helps.