Direct3d problem with old laptop

I have an Inspiron 9400/E1705. When I go to the Dell Drivers and Downloads page, I can't find any driver (under Display or Video) that seems to apply to my system. When I tried this search a few months ago, I found a different list offered and the only video driver was dated 5/14/2007 (although the driver it actually installs is dated 3/30/2007).

I bought this laptop second-hand and the previous owner had somehow managed to find a way to get Direct3d to work because I was, for a while, able to run games and applications that required Direct3d (for example, Google Earth). But then I made the mistake of updating the display driver. Ever since then,  I get messages about not being able to access Direct3D. When I run Dxdiag, on the Display page, it says "Direct3D functionality not available.  You should verify that the driver is a final version from the hardware manufacturer."

Is there a more recent driver that includes Direct3D? If so, where can I find it? If not, how was I able to run those games before and can't now?

TIA