Windoor is a 3rd party plug-in for VectorWorks. This means that you might have to go to the internet and buy this from the producer.
If you are in NZ or Australia you will have this already. If you are located in another part of the world then you will have to visit this web site to purchase it http://www.ozcad.com.au
I have been using Windoor for several years and I like it a lot.