Support for the venerable Windows XP operating system ends Today.
It means that there will be no more official security updates and bug fixes for the operating system from Microsoft.
Some governments have negotiated extended support contracts for the OS in a bid to keep users protected.
Security firms said anyone else using the 13-year-old software would be at increased risk of infection and compromise by cyber-thieves.
Statistics suggest 20-25% of all users have stuck with XP despite the fact that there have been three major releases of Windows since its debut in 2001.