Updates do not install after a Repair of XP
Updates are not installed successfully from Windows Update, from Microsoft Update, or by using Automatic Updates after you repair a Windows XP installation
The issue occurs because a file left on the system during the repair installation no longer has a corresponding entry in the registry.
To resolve this, open a Command Prompt, stop the Automatic Updates Service, register the file, and then restart the AU Service:
1. Stop the Automatic Updates service. To do this, follow these steps:
a. Click Start, click Run, type cmd, and then click OK.
b. 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:
a. 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
b. 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
4. Exit the command prompt. To do this type exit, and then press ENTER.
I haven't run the commands yet but will do so to find out if just running
regsvr32 wups2.dll will accomplish the same task.