I just installed an NVidea GeForce 210 in my Dimension E510. Installation went smoothly, but after everything comes up there is a ~1/2" square in the middle of my display that always shows the background. Open an application and I have a little square window through which I can see my desktop. If the application updates its display the square immediately comes back into view.
Switching monitors makes no difference, I exchanged the 210 adapter (Nvidea felt it was defective card), uninstalled and reinstalled the drivers, updated them, downloaded the latest BIOS and chipset updates from Dell, tried different display resolutions ... no difference.