RenatoServos,
When I'm really frustrated with a problem, I find that sometimes I'm just thinking too hard and just don't see clearly. I try the following: Take a step back, relax, then realize that maybe the problem is not what we think it is. I use Norton Ghost to create an image of my current system so that I can easily re-image back to where I'm at. Now, just maybe the problem is a conflict with something else rather than the ATI vs O/S. Since I have a ghost image that I can restore in a matter of minutes, I now start fresh with a clean install of O/S and let ATI video temporarily pull generic video drivers from Windows installatin. Next, Perform windows updates. It seems to me that I remember from somewhere that ATI video requires latest directX be installed PRIOR to the ATI video drivers. I think I also remember something about directX ver 8.0 required something additional but that ??? whatever it was is not needed with directX 9.0b, it's included within 9.0b. Now, hopefully with clean O/S, latest windows updates including directX have been installed, my installation of ATI video drivers and video applications will work. If this is true, problem is conflict with something else. Install rest of items one at a time testing after each individual install until the problem presents itself at which time that should identify the culprit.
If you don't have Norton Ghost, perhaps you have a spare Hard Drive so that you could remove your current hard drive temporarily, then try a clean install as described above, on the spare hard drive, thus preserving your existing installation.
I hope this method solves your problem. Good Luck