Anything Related to this?

So, about 3-4 days ago I have installed a new video card and PSU (Power Supply Unit) into my machine with little to no difficulty. At the beginning setting up my video card was a pain and some of the games I love to play now won't run because of it.

The video card I am using is an ASUS EAH5450 512M DDR2. A product of Radeon. Only after getting it though, I've been told that ASUS is no good. After the most recent patch, I logged in to the game once, and played. No problems whatsoever. About 18-22 hours later, I try again and I get this error window telling me an external program is preventing the game from operating/running.

Take a look:

I've tried following the steps from support.microsoft but that really didn't help at all.
If you guys can tell me what kinds of programs prevent the game from running, that would be a big help.