Error activating Microsoft Security Essentials

I'm installing MSE on a XP Professional SP3 PC. After the initial install and update, an error pops up:

Microsoft Security Essentials cannot start real-time protection
This operation has been cancelled due to timeout error
Error code: 0x800705b4

I'm translating from the original spanish error message:

Security Essentials no pudo activar la protección en tiempo real
Esta operación ha regresado debido a que el tiempo de espera ha caducado
...

I tried uninstalling / reinstalling with no luck, all the posts I found on the subject suggests problems with active malware or posible interactions with other anti-mailware software: it isn't my case, I did a fresh Windows XP SP3 installation before install MSE.

I believe the update is failing and timing out is due to the fact there is no server/service to answer the request. The problem is the fact you are trying to install an unsupported product on an unsupported operating system. Support for Windows XP ended on April 8, 2014. Not only that, Microsoft Security Essentials was replaced by Windows Defender long ago. The only operating systems that Microsoft still supports Microsoft Security Essentials on Windows Vista and Windows 7. When those go out of support, MSE will be gone with them.