virtual Display driver in vista

Hi,

I am very new in driver development for Vista. Presently I am working on XP display driver stack. In XP I am able to develop our minimal display driver to support some specific feature like rotation etc.
The same thing I want to do in vista. Problem is vista has WDDM display stack so our XPDDM driver will not work provided we forcefully enable it but in that case we will not have the aero effects.

Recently I have seen the DisplayLink's driver stack for vista which is supporting mirror and desktop extension mode for USB monitors.
I have little bit analyzed the drivers and found that it is probably using it's own display adpter driver and mirror driver but once I see the properies of display adpter [ right click-> display properties] it shows vendor driver only. So I am suprised that how display link is supporting all these features [ mirror and extension] in all modes [ aero and non-aero]?

Please show some light in this direction? Bcoz I am stuck here and don't know how to proceed further.

Thanks in Advance
Harry