When you try to install updates from the Windows Update Web site, from the Microsoft Update Web site, or by using the Automatic Updates feature, you receive a message that states that the update or the updates were not installed successfully. However, the updates are not displayed in the Update History part of the Web site.

Method 1: Register the Wups2.dll file in Windows
To register the Wups2.dll file in Windows, follow these steps:

1. Stop the Automatic Updates service. To do this, follow these steps:
   Click Start, click Run, type cmd, and then click OK.
   At the command prompt, type the following command, and then press ENTER: net stop wuauserv
 
2. Register the Wups2.dll file. To do this, follow these steps:
   At the command prompt, type the following command, and then press ENTER: 
       regsvr32 %windir%\system32\wups2.dll
 
Note: For a computer that is running Windows XP Professional x64 Edition, type the following command, and then
   press ENTER:regsvr32 %windir%\syswow64\wups2.dll 
 
Click OK on each verification message that you receive.
 
3. Start the Automatic Updates service. To do this, type the following command at the command prompt, and then press ENTER:
net start wuauserv
Exit the command prompt. To do this type exit, and then press ENTER.

Method 2: Download and install the Windows Update Agent
To install the latest version of the Windows Update Agent, we recommend that you visit the following Microsoft Web site: http://www.update.microsoft.com

When you visit this Web site, the latest version of the Windows Update Agent will automatically be installed.

Additionally, Microsoft has also made version 7.2.6001.788 of the Windows Update Agent available on the Microsoft Download Center.