As I said in an earlier post, having Autodesk Design Review 2007 be free is intended for customers until Autodesk Design Review 2008 is ready. As a product that was designed to be free from its inception, Autodesk Design Review 2008 will not require a serial number. Since Autodesk Design Review 2007 was originally released as a for pay product, it does require a serial number. We have provided serial number 400-96523577 for this purpose. This serial number is only necessary for install. You do not need to register Autodesk Design Review 2007 for it to operate. In fact registering it fails, since the serial number has already been registered. So please use the serial number for your installation but skip the registration step.