If you have manually downloaded and installed the patch for MS05-050, you may want to check again to make sure you have the correct patch. Microsoft has recently released a Knowledge Base article on "The computer may not be updated after you install the "Security Update for DirectX 7.0 for Windows 2000 (KB904706)" on a Windows 2000-based computer that is running DirectX 8 or DirectX 9".

According to the Microsoft, this only applies to:  
? You are running Microsoft Windows 2000
? Microsoft DirectX 8.0 or DirectX 9.0 is installed on the computer

This is likely due to the incorrect patch that you have manually downloaded and installed. If you have installed using Microsoft Windows Update website, you should be protected and free from this problem.

To check whether your system is correctly updated, you can verify the version number of Quartz.dll. The steps are detailed in Microsoft KB article 909596.