Hi Maggie

If I were to make a guess, it could be a video card problem? Depending on how old your computer is, that is...and if it has a videocard on its own.
The Ethernet card is a network card, as I remember it, it is unfortunately not a graphics card.
Is your computer a desktop or a laptop?
Did you remember, Maggie to install the game into another location that C:/Games Programs. In Vista older games like TLJ doesn't like to be placed in the program files folder since Vista sort of locks this folder (for security reasons). Have you tried uninstalling the game - and then installing it again in a folder called Games.
[To create a new folder right click on blank page on your desktop then new then folder - then rename this folder - Games. To rename the folder rightclick on the folder and go down to where it says rename and type the folder name e.g. Games].
To check if your computer has a stand-alone videocard, please rightclick on the My Computer icon, then select properties, and then on the next screen, please clcik the Hardware option, then on the next screen click on the first (top) available option. You'll come into hardware management; please scroll down to where it says graphics or screen card. Now please click on the x (the mark) in the box next to it, and see what it says. Mine says this: ASUS AH 3650 Series.
I really do hope you get TLJ to work.