If the lights are "off," they're not doing anything but eating up little bits of memory. They're left over from whatever light set you'd loaded or created before the current one. If, like me, you're using Poser 4 without ProPack, you have to deal with these things manually. That's why I try to get everything set up first, adding lights last. If you want to experiment with different sets, start with the ones you know to have the fewest lights before moving on to things like global sets. That way, if you choose to delete residual "off" lights, there will ideally be fewer to deal with.