Vista - ATI 9700-pro 128mb agp card high temp

Ever since I've been using vista build 5384 I've used an Nvidia n6200 256mb
agp card and it's been great Aero works perfectly with it
I also have an ATI 9700-pro I decided to try it out with windows vista
I have a dual boot system with windows Xp pro as my main OS, firstly I
booted to XP pro the card ran perfectly
Then I booted to windows vista the card also ran perfectly aero worked
straight away my performance rating went from 2 to 3 however after about 30
minutes the card started overheating and artifacting
So I booted back to Xp pro with it, without letting it cool down, and it was
back to normal again I played Doom3 with it, for 39 minutes without any
trouble at all.
But back in vista it artifacted again after about 30 minutes
Has anyone else had this issue?
Or is this simply because windows vista uses more resourses form the video
card than windows Xp ?

> ..... however after about 30 minutes the card started overheating and
> artifacting
> So I booted back to Xp pro with it, without letting it cool down, and it
> was back to normal again ...
RMA the card back to ATI for free replacment.