UAC and Window Prompts Odd Looking

I recently reformatted Vista because I had gotten a new motherboard and
processor. Ever since then, my computer has been running great with Vista.

My only problem is that whenever a UAC Prompt comes up (or a "Windows"
prompt such as scanning the system for a new rating) there are a good amount
of black lines through the window. It is usually just through that prompt
window, nothing else. If I move the window, it will do some kind of drag
effect and make slight copies of the window around the screen.

My system specs:
GeForce 7800 GS
Intel Core 2 Duo 2.2 ghz processor
1.25 gb of ram