"Full screen mirror" Geforce 8 series

I have just purchased the Geforce 8800GT, upgrading from my old 7800GTX, now I have just found out nvidia does not support "full screen mirror" option in either xp or vista in the 8 series card & apparently this is hardware based. I used to use the option alot for working on my PC & letting the kids watch a movie or vids playing on dualview directly on my plasma.Going by alot of forums this has pissed alot of people off. my question is does the oppositions platform (ATI) still support this option? In the 3850 or 3870, because if it does I will change, but I want confirmation before changing & no one so far can tell me. I was using latest forcware which did not option full screen mirror, but i did a regedit to convert back to old NV control panel but option does not work. any help most appreciated.