I have installed everyone but this one. I tried installing it by itself and get the same error. Here is the details screen view:
Update for Windows Vista (KB941649)
Installation date: 4/2/2008 10:33 AM
Installation status: Failed
Error details: Code 800F0826
Update type: Recommended
This update resolves some compatibility and reliability issues in Windows Vista. By applying this update, you can achieve better reliability and hardware compatibility in various scenarios. After you install this item, you may have to restart your computer.
More information:
http://support.microsoft.com/kb/941649
Help and Support:
http://support.microsoft.com