No, I don't think the 4D Viking software can be registered anymore because the official website lists a new version. The software is called 6D™ Embroidery. There is a link for this version on the Support page, but it leads to a page that doesn't load.
It's possible the developers might offer this product privately which means you will have to get in touch with them in order to find an answer: Http://www.husqvarnaviking.com/Support