Direct3D 6? Wow, the game must be way older than your computer. You probably installed DirectX 10 or later. There were major changes after DirectX 9. The software routines to manage graphics hardware acceleration through DirectX 10 or newer are probably very different from DirectX 6, so the game's graphic controller interface can't find them.
Try going into the game properties (right-click on the main executable file and select Properties from the pop-up menu).
Set it to run in XP compatibility mode and see what happens.
Check to see if the game has the option to run without hardware acceleration. If this provides acceptable performance, that is your answer.
If necessary (and if Microsoft still makes it available), try installing DirectX 6. Vista may snag on it and make you remove it and reinstall a newer version, but it's worth a shot if the other fixes don't work.
on Jul 03, 2017