Help with Doom64TC

OK, so I have DirectX 8, and I also have the Doom64TC. I really want to play this, so I load it up in Opengl mode, I get as far as setting the controls, loading up the first map on skill 3, and then the damn thing goes back to the desktop. It does every single time I try to play the game, and Direct3d won't work at all. I get the good old "failed to iniatilize Direct3d" error. So, I'm stuck here.
What do I do?

My specs are as follows:
PIII 450
Voodoo 3
64 megs Ram

Yeah, it's kinda old, but I know it works, because I remember playing Doom64 for a couple days before the last time I formatted. As I recall, it was quite fun, and thusly, I want to play it again.
Any help would be appreciated.

Heh. Doom64 doesn't like to be edited. At least not in my experience. :P

But, I didn't edit it!

Do you have an existing copy of doom2.wad in your absolution folder?