In rare cases, unused legal licenses for older software like Inventor 2013 might be available through authorized resellers (though most have moved to subscription models).

That being said, here's a general guide for users who are looking to activate Autodesk Inventor 2013 64-bit using an Xforce Keygen:

If you are facing the "Registration Activation Error (0015.111)" on a legitimate copy, common fixes include: System requirements for Autodesk Inventor 2013 products

If you need to use Inventor 2013 or a more modern version, consider these safer methods:

Always ensure you're using software in compliance with legal and licensing agreements. If you're unsure about the legitimacy of your software or activation process, it's best to consult directly with Autodesk or an authorized representative.