Autocad Civil 3D Portable is a modified, "no-install" version of Autodesk's flagship civil engineering software, designed to run directly from a USB drive or external folder

Do not use Portable Civil 3D for professional work or projects you cannot afford to lose. If you are a student, get the free educational license. If you are a professional, the risk of data corruption and liability far outweighs the cost of a legitimate subscription.