How to install and update a patch after XP has SP3 installed

XP cannot be updated after SP3 is installed
Register wups2.dll in Windows File
To register the wups2.dll file in windows, follow these steps:
1. Stop the automatic update service. To do this, follow these steps:
A. Click Start and run, type cmd, and click OK ".
B. at the command prompt, type the following command and 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 press Enter:
Regsvr32 % WINDIR % \ system32 \ wups2.dll
Note: For computers running Windows XP Professional x64 Edition,
Enter the following command and press Enter: regsvr32 % WinDir % \ syswow64 \ wups2.dll
B. Click "OK" on each verification message received"

3. Start the automatic update service.
To do this, enter the following command at the command prompt and press Enter: Net start wuauserv
4. Exit the Command Prompt window.
Install patches.