Well, after months of trying to find the problem, I solved it.

I had to buy a new hard drive (old one crapped). But I now have a solid state digital hard drive, much faster. Also, I bought a AMD Radeon 5450 (the Dell mentioned above would not have been compatible with my motherboard and would have needed more power). At first it wasn't giving higher resolution, but I went and downloaded the new test version of the Graphic Rules Maker and it worked. I set both my Default resolution and Maximum Resolution in the GRM to the highest resolution and that worked. I also bumped up the forced texture memory to 128mb. Now, I'm in the process of rebuilding my files for the game. I'm being very careful about what I'm downloading using Clean Installer every time I put new content in.