Starting April 8, 2014, Microsoft will cease to provide hotfixes, product updates, and security patches for Windows XP users. SP3 is the last service pack for Windows XP, with its support ending on April 8, 2014.
At that time, Microsoft may also stop providing MSE updates for the XP platform. The full name of MSE is Microsoft Security Essentials, which is the free antivirus software released by Microsoft for XP, Vista, and Win7.
A Microsoft spokesperson stated: "After Windows XP reaches the end of its lifecycle on April 8, 2014, Microsoft cannot guarantee updates to antivirus signatures and engines. Running antivirus software on an unsupported operating system cannot protect users from risks."
"To obtain robust protection, the first step should be using modern software and hardware that can help you defend against today's threat landscape. Microsoft also recommends adopting the following measures to protect your PC: 1) Run the latest antivirus software. 2) Regularly perform security updates on all installed software. 3) Use software supported by advanced security technology and regular security updates."
It is not surprising that Microsoft will stop updating MSE for XP in April 2014. If you insist on using XP, you can consider other antivirus software options. Third-party antivirus software vendors are unlikely to abandon support for XP users as Microsoft has.