If the software is still installed on an old computer, you can use "product key finder" utilities to extract the key from the Windows Registry.
The primary role of the product key is to transform a trial or limited-use installation into a fully functional "Retail" or "Professional" version. While Microsoft permitted users to open Project 2007 programs up to 25 times without a key, the software would eventually enter . In this state, critical features such as saving and printing projects are disabled, effectively rendering the tool useless for professional deliverables. Locating and Protecting the Key
: A free utility that retrieves product keys from the registry. Important Considerations MS Project 2007 Key - Microsoft Q&A