http://www.blizzforums.com/history/topic/14864-1.htmlPosted by: Firestorm
Hi Tokidaze, DirectX cannot be uninstalled manually through the control panel. The only way to completely remove DirectX without formatting is by using a free third party user created application. These programs are small in size and are typically downloaded as on Executable. Once run, they will remove DirectX from the registry thus allowing you to-reinstall a previous version of DirectX.
Use the application found in this link to remove DX9 from your system. Please also ensure that prior to running this application that you backup any important data.
Download link:
http://www.majorgeeks.com/article.php?sid=2935In the future it is always recommended to disable all third party applications while downloading both NVIDIA Detonator and DirectX drivers as this can often cause the downloaded file to become corrupt.
Please let me know if this helps you out.