Most graphical problems folks have with FF7 on PC anymore involve outdated architecture. FF7 is an ancient game by modern graphical standards, full of things that newer graphics cards just don't bother to support anymore. What this means for you is that there isn't much you can do about it. Again, though, i'm just guessing.

Go to http://ficedula.cjb.net/ and download the "Cetra" utility. Run it, activate "Debug" mode, and then run FF7. It'll create a file called "app.log" in your FF7 directory, and that file might tell you what specifically is going wrong. i don't know much about the program itself, because i don't have FF7 for PC and thus can't check it out. But it's the best i can give you for now.