This was implemented by MicroSoft, but not as a seperate nor fully featured Driver.

Rumors had it, that MicroSoft pressured support from Nvidia to aquire at least a functional WHQL 2D DirectX Display driver, and apparently NVidia delivered.
After all, at that time there were still a handsome number of 3dfx Cards in operation, I imagine lacking any WinXP support would have threatened to decrease WinXP sales.
(even much older vintage PCI cards have proper WinXP 2D default Drivers, so leaving 3dfx out completely would have been a rare and undesirable exception)

But still, it's just the plain 2D core (as far as I know), I believe it has no Direct3D or even OpenGL functionality at all.

..and no SLI for voodoo5 .it has a limited d3d functionality though.