Well, I have heard some people complain about Cataclysm being demanding, but I have an ancient HD2400 PRO with 2Gig Ram on Vista and it runs okay (30 FPS) on medium-low settings at 1024*768 for me.
So, I'd imagine you would be able to play on high settings at 1920*1080 without any problems. Just tweak the multi-sampling, draw distance or shadows to get the optimum balance of performance to eye candy as they make the biggest difference.