The older drivers were still supported under Vista, but since the older model did not encompass support for features first introduced with Vista, those newer features would necessarily be disabled when an older driver was active. As a consequence, when a mirror driver designed for the older model was active, such as when Windows Remote Assistance or Windows Live Mesh were in use, Vista disabled Desktop Window Manager and Windows Aero.
Older drivers continued to operate under Vista, but because they didn't support features introduced with Vista, those new features would be disabled whenever an older driver was used. Specifically, when a mirror driver designed for the older model was active, such as during Windows Remote Assistance or Windows Live Mesh usage, Vista turned off Desktop Window Manager and Windows Aero.