I was vaguely aware that there was something in this space already... I think it used be known as Virtozzo? Anyway, I wonder how well it can work as a layer on

I was vaguely aware that there was something in this space already... I think it used be known as Virtozzo? Anyway, I wonder how well it can work as a layer on top of the Windows OS rather than being integrated as I imagine only MS could do.