If your copy of VCarve is not registered to you I don't think you will be able to upgrade it, so you would be looking at purchasing VCarve or Aspire new. Can you get in touch with he original owner and transfer the registration?
Otherwise there are numerous option out there for 3D design-Rhino, MOI, Blender... As long as they can export a file format that your VCarve can read like STL you can run it. That said Aspire is your best bet as you can build on your experience with Vcarve. The true cost of software is a lot more than the purchase price if your time has any value.