Okay, this is something that isn’t supported by Microsoft in any way and they might close this workaround in the near future.
After more than 12 years, Microsoft stopped the support for Windows XP. But for companies that were unavailable to upgrade to a later OS were given the option to get updates until 9th of April 2019, in exchange for hefty fee.
To get the updates, you must trick Windows XP into thinking the OS is Windows Embedded POSReady 2009. Since these updates are based on Windows XP SP3 they are the same that should have been deployed to Windows XP SP3, if it was still supported.
What you need to do to achieve this, open regedit as administrator and browse to:
The key PosReady might need to be created.
Under PosReay, create a new DWORD, name it to “installed” and give it a value of 1.
The restart the computer and you should see just above 100 available updates.
Even though this works at the moment, I still recommend that you upgrade to a later OS fo security reasons. A lot has been updated in Windows 7 for example, and even more in Windows 8.
Also, as mentioned earlier, Microsoft might shut this workaround down in the near future without warning!