Well I tried Cross Fire today. When I tried booting up the XP screen just froze. I thought maybe my Corsair 750TX wasn't able to handle the electrical demands of these cards when ran in CF mode. So I took one card out and the system would not show any display or post. Only the VGA fan spins.
Then I tried the other HD4870 and the same thing happens.

I then tried all of my old VGAs and everything runs fine.

Therefore, i tried each HD4870 in my other systems and only the fan spins and no display output happens.

I don't know what happened, but it's RMA time. At least I got to play with 1 card for 2 hours.