OK, I found a way to change the default windows voice.
It's by having VoiceAttack run a ahk program.
When you run it, a menu opens, and shows you a list of all your voices you have installed. Each Voice has a number beside it. You type the number for that voice, and hit Enter, or click Ok.
In this case you want to hit Enter.
I made a little command, that will run the ahk program, and enter a number and hit Enter to change the voice.
You can have this program run, and set a voice for each app you go into.
Or you can make a command name like, "Change to Amy" and it will change the voice to Amy.
Below I've attached two files.
1. Change Windows Default Voice-Profile.Vap ;Profile that has the command in it. Just import in it into your profile.
2. Change Windows Default Voice.exe ;This is the AHK program, put this in your VoiceAttack Apps directory. c:\Program Files (x86)\VoiceAttack\Apps\ ;This is usually the default path.
Once you have Change Windows Default Voice.exe, run it, and you'll see the menu with the numbers and voices, make a note of what number is what voice, and then change the command to match the voice you wish.
Nice little program.