Some serials of Py4D will expire within the next days. If you have such a serial you can create a new one which is valid until August 27, 2009.. If Py4D expires(0 remaining days) you will get a serialbox where you can paste your new serial. Just wait until you see the serialbox, visit this link and follow step 3. Its recommended to download the new version of Py4D (v0.9.8400).