Yea, my issue is that I don't have another computer, or access to another computer to really test anything using hardware.
Another issue is this problem only occurs maybe once every 2-5 days. Even if I swap in another video card, I wouldn't really know whether that specific action solved the problem because the problem usually resolves itself right away anyway.
Do you have any exceptionally demanding (by the standards of the hardware) game? Usually a bad video video card will start messing up once it's put under significant load. If it only happens at start up and not when the card is under load, something else may be at fault.