You can't obtain the software any more because this was bundled with the CDs that arrived with your PC. Nowadays, the product appears to be discontinued which means you will have to obtain other applications from the same category if you want to enjoy the functionality offered by MyDVD. Luckily, there are plenty applications like MyDVD.
For example, there is an application called ProShow that allows you to add music, videos, images, etc and then burn them directly to DVD with DVD menu support.
You should give it a try using the following link: http://www.photodex.com/proshow