Sure its not the fan in the PSU? Random noises in pc cases can be so frustrating, in the past few days smoething started making a noise that sounds like a fan though doesn't seem to be any of the fans, I think this one is actually the PSU starting to go bad, though it could be the PSU fan but because of the angles and a huge tower heatsink I can't get anything like a pencil in to stop the fan to see if the noise stops.
its odd how you can stick your head almost right into a case and still not be 100% sure where the noise is coming from
Its possible its the PSU fan spinning up higher/harder than ever before if you've never had a card that uses as much power as the 4850 so the PSU is hotter than ever before and fan increases speed as the load or temp does.
I have to say that I've had lots of cards that others appear to have had capacitor squealing with and I've never experienced it to date, but have always had a more than decent PSU with ample headroom(currently a 1kw Thermaltake toughpower, I got it for a steal at £90 and at the time was one of the most efficient out there and still is VERY good).
I'd say a 430W isn't bad, and its a good make, but depending on what cpu/memory/hdd/fan setup you have you're unlikely to be pushing the limit but might not have that much headroom, people also say PSU's do degrade over time and won't be rated to the same power after 3 years so a new PSU might not be a terrible idea anyway and might fix it.
I'd also just double check with vsync in WoW, there should be an option in the WoW options in game to enable vsync.
Vsync and triple buffering in the control panel are for opengl only as "officially" MS doesn't allow the options to be in drivers for directx games for some ungodly reason, well basically DX games don't have to support vsync and trip buffering so WHQL approved drivers can't have the option or something ridiculous. So unless the game offers it you sometimes have to use dxoverider or one or two other apps to force vsync and trip buffering in some games.
Any chance you could try it in any pc's of friends of family? If anyone has a half decent computer you could try it in, if it works fine with no squealing it would probably point more towards the PSU than anything else.
The absolute worst thing when these things happen, is when its just coincidence and after lots of messing around and changing things and upgrading, it turns out to be something ridiculous and nothing to do with the gpu/psu.
