Stellar Phoenix JPEG Repair has a very simple and user friendly interface that helps you repair photographs or image files that have been corrupted.

On launching the program, you get a window as shown below:

Under Tools menu, find the option Register - use it to activate the software.

Registration window is displayed. If you have purchased the product and received the registration key select 'I have a key to register the product' option. Click OK. In the Registration Key box, type the key. Click OK. Alternatively order Stellar Phoenix JPEG Repair software.

Registration key I've entered is reported as invalid.