Try this and let me know how it goes.
Make sure to install the monitor driver as well. It makes a big difference 100%.
I've tried that driver before, both with Vista & 7, and I have installed it now without results. My monitor driver is also installed and in use.
I told you all the suggestions that I did recently and it worked fine in my case. Hope someone else can help you on this one.
I remembered a weird step that I did on another system, and i managed to get different resolutions. I uninstalled the graphics driver and used the default driver and it worked fine.