I noticed the same thing when I upgraded to the Asus A8V Deluxe with AMD XP 64 3800+, ATI X800XT PE from my Asus A7V Deluxe AMD XP 3200+, ATI 9800XT PE.
At least I now know that I'm not the only person that did not really gain from the upgrade. I am beginning to think that there is something with the Asus A8V Deluxe board that needs changing, but inspite of all the research I have done, I still have not found what it is yet.

And I did reinstall Windows too.