As of April 8, Microsoft says it will retire its old, dependable operating system, which first shipped in 2001.
Greg Sullivan, Microsoft's director of Windows, says "We can't continue to support it forever."
Sullivan says it's a standard industry practice to retire operating systems in the constantly evolving tech world. He points to Apple's recent decision to end support for its Snow Leopard operating system, which shipped in 2009.
XP users are being asked to go to AmIRunningXP.com for information on how to upgrade their systems.
Microsoft is encouraging its customers to upgrade to its Windows 8 operating system, which has received mixed reviews.