masha, You don't need a challenge code... that was taken care of in the second SR for Poser 5. Go to the CuriousLabs website and download the updates to get SR4.1. Read the readme to fix a small thing with background color in one of the rooms. You might also need the figures updater which came with SR3. (I don't know if SR4.1 includes it.) Anyway, get the patches in hand. Having downloaded the stuff... reinstall P5 (you may want to copy over your Runtime to a safe place, and remember that you can link them). Do NOT open it!!! Install the updates. Restart the computer. Some of us restart between each item just to be sure that Windows catches it. You should now be able to just type in your serial number and be good to go without the challenge code. Carolly