There are dozens of reasons to abandon Windows XP (security, technical, …), but if you have no option, at least you can mitigate them by enabling the PosReady option and installing all MS published security updates.
Open Registry Editor and go to:
the add/edit the value ‘Install‘ as DWORD and set it to 1.
Reboot, and run Windows Update by the following command line:
It should find more than hundreds of items to install.
PS: From April 2019, even MS Security Essentials didn’t update its definitions anymore.