None that i know of, im running a HD3850 on Xp at the minuite.
Couple of things,
First why a 1GB card ? The card has a 128 bit bus and as such cant really push the resolutions where the extra Ram would be used. Which leads to point 2 which is your display and resolution, as i said already the card wont push big resolutions due to the bandwidth limit so if you are planning on running a big screen then you need to be looking at a card like a 4870.