Graphics problem

[CivLuvah]

Hi there! I have a graphics problem in my system. Every time I build a wonder, the wonder movie doesn't work properly. plus every time there is a wonder movie, my computer screen suddenly goes black & sometimes the computer resets itself. can anyone please help me with this graphics problem? my computer is very slow and my computer resolution is 800x600 but sometimes when i play Civ4, my computer resolution turned into 1024x768