I don't think it's possible to download the product anymore. I've searched on various websites and didn't find anything about it. No download link is found anywhere.
You can try to see if you can download a copy of the Cakewalk Pyro 2004 with the help of Cakewalk Command Center which offers the Cakewalk products for download, but isn't guaranteed that it will contain the download for the Pyro.
It's best to simply get in touch with the developers to ask them about this.
