If you are still running Windows XP, then you haven’t received any security updates for the last year since support ended on the 8th April 2014. The updates are normally released once a month on “Patch Tuesday”; in March alone there were 14 separate security updates.
If you are still using XP, then you are at increased risk of getting a virus or other malware, antivirus alone cannot protect you as it is imperative that your operating system and other software are fully up to date. If you use your XP computer for online shopping or banking then you are at much greater risk of a “man in the middle” attack, which means your encrypted data sent to these sites is intercepted by a third party.
If you haven’t upgraded, then it is time to reconsider. There are many options available to upgrade to a more modern and secure operating system, it doesn’t have to cost a fortune, there is an option available for all budgets, including a low cost refurbished system.