Official statement:
We inform you that since July 25, 2019, Wargaming (completely, comprehensively) ceases to support Windows XP and Windows Vista. To continue using the company’s products, you need to install a more modern operating system. If you cannot upgrade Windows XP online, you can use the temporary alternative method to start and update World of Tanks.
How to continue playing on Windows XP –
How to play on Windows XP
We have stopped official support for Windows XP. However, we want users who do not have the technical ability to install a more modern operating system to continue to play World of Tanks.
To run the game on a computer running Windows XP, follow the instructions:
Download the RestoreLauncher app.
Close Game Center.
Unpack the application to the game folder (for example, D: Games World_of_Tanks).
Run the application.
When the installation is complete, an alternative launcher will start.
Now you can play World of Tanks on Windows XP.