Tulivu: I wish there was a real video game equivalent to the tabletop game. I always wanted to play but the idea of purchasing a working army and trying to find time with the local community put me off. I almost bought a Grey Knights set but I put it off (funny, it was just before I joined a different Marine Corps). When I get a working gaming computer again, I'll have to get DoW but its just not the same.
Check out Vassel40k. It's pretty much exactly like the table top, just play by e-mail or real time. It's not pretty, and you'll need the rulebook and the codex for the army you're playing, but it gets the job done.
My friend and I played a match using it, and once we figured out what we were doing it was fun.