First off, what executable are you using? Have you patched it at all? Is it the executable from the 1.02 update?
Did you run FF7Config after installing the driver (this can uninstall it)?
You installed the regular reg file, not the Vista64 one, right?
You unzipped all the driver files into the same folder as ff7.exe, right?
Edit your config to set fullscreen to false, so it's very obvious when the driver is working and when it isn't.
If nothing there fixes it, run FF7Config and make sure everything works there (don't worry about the graphics tab), then reinstall the reg, then make sure the config has fullscreen set to false, then run ff7.exe. If you still get a fullscreen game, post your APP.LOG.