Hi I have just installed a HD5770 and when I start windows, after the accounts screen the screen dims slightly (not loads but enough to notice the dark screen). It does this on every account. I have tried Driver Cleaner Pro and reinstalled the drivers. Also when I power up, the windows loading screen jumps once (as if refreshing) and also when logging off the screen goes blank for a second before returning to the accounts screen. I tried putting my old card back in (a HD4650) and everything goes back to normal. Cant figure it out, the only thing I think it could be is the minimum PSU recommended is a 450watt, mine is a 400watt, but it is a corsair and I have read that this card will run with this psu. I dont have loads of drives and using a power calculator I am only using about 333watts. Hope you can help before I send this card back and revert to my old HD4650 Cheers.