you've got the correct dx9. I'll post up a quick guide for winXP users to completely get rid of ATI drivers on their system so you can install the driver of your choice on cleanly. If it looks like too much don't sweat it! And hopefully, you've got a restore point set anyway before dx9 that you can roll back to if need be...
we need to get rid of or "clean" your system of all previous ATI stuff. including the ATI junk that comes complimentary with winXP SP1

heres what ya need to do:
1. unplug nic card or modem from net (physically unplug)
2. create system restore point (if you don't already have one)
3. remove ATI driver from add/remove programs then remove CP from add/remove programs
4. reboot into safe mode (press F8 during boot up)
5. if you've never deleted the ATI inf files from windows (ie search ati*.* and delete) or if you're connected to the net, you'll not be able to cancel out of windows automatically finding new device and installing drivers for it. Let it do it's thing, we'll fix it in a minute heh.
6. Open windows explorer and delete c:\ATI and c:\program files\ATI
7. start->run->search c:\windows for ati*.* and delete all
8. empty recycle bin
9. open
regedit (great, must have program!) and delete any ATI (usually 3 together and then one or two in separate places... like one under Installed options for example). That sends them to backup. Then go to backup and select and delete again.
10. close regedit
11. open device mgr->display adapters->uninstall and reboot
11. you should now come back up into windows and if you're unplugged from the net and have searched and fully deleted (emptied recycle bin) all ATI*.* files, you should now be able to cancel out of windows automatically installing your video card drivers. Just cancel out. If you have dx9 on already, go to step 14
12. I would now install DX9 if you haven't done so
13. reboot for dx9 sake
14. install official catalyst 3.0 drivers and CP