Malformatted webpages

I came across the most patient client on the face of the planet. She reports for the last couple years her webpages are not formatting correctly. For example at www.southwest.com she is missing the ginormous picture on the left side. At MSN's homepage the buttons don't format correctly. Both in Firefox and IE. I would have thought it was just the page if it was just one, or just the browser if it was just one. But! Safari renders correctly. I don't even know what possessed me to try Safari, but it worked. Have you guys any idea what's going on? She's tried ripping and reinstalling, we've tried a couple different versions... I know it's obviously not the page since the desktop adjacent to the problem pc is rendering just fine. I thought it might have been a problem with .gif (which is what the pic @ SouthWest is) , but she is rendering other .gifs. She does not get the frame with the red X, she can follow links that were embedded... I just don't know what else to poke.

I've attached screenshots of her FF and IE, and her msinfo32 for the obvious necessary info.

Any help you could send my way would be greatly appreciated!