It has nothing to do with the monitor i think. Resolution/refresh rate can be the problem, maybe vertical sync. Try variating these, and make sure you use your new monitor's native resolution. A gt430 shouldn't have any problems with a game like war3, and i guess you have a decent cpu for this card as well, so the problem must be some settings related. Also you should turn off aero in win7, sometimes it consumes shitloads of resources.