I just fixed it...
Copied
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:metro="http://schemas.codeplex.com/elysium"
xmlns:params="http://schemas.codeplex.com/elysium/params"
params:Design.Theme="Dark"
params:Design.AccentBrush="{x:Static metro:AccentBrushes.Blue}"
params:Design.ContrastBrush="White"
Title="MainWindow" Height="600" Width="525" ResizeMode="CanMinimize">
from main from that works perfectly over to the form that complained.
and I can change what form I want to start with running using the App.xaml