Hello Sir, Thanks for you using CADian. All serial No. starts with alphabet I. 1. If you are commercial user with package box, you can find serial No. on DVD case in box. 2. If you are commercial user with download, you can find serial No. from your dealer or through your email that you got [download] files from dealer. * If any, please let us know your copany name. We will check our database and back very soon. * If use a trial version, you can use CADian 2014 during 30 days without serial No. Please feel free to contact us if any. Regards, CADian Soft