What does this mean?
You don’t get security updates anymore, vulnerabilities will not be fixed, so your system is a sitting duck.
No virusscanner or firewall can save you.
What to do now?
Replace your XP with an operating system that get security updates as soon as possible. In fact you should have done this a long a time ago …
Is there an alternative?
Yes, there is, it’s called Linux :
Linux is a free and open source operating system ( it means you can download it for free, share with your friends or even alter it the way you want to ), it’s reliable and sturdy.
My favorite is Debian GNU/Linux, but if you’re new to Linux I suggest Linux Mint LTS (based on Ubuntu LTS). An other good and reliable distribution is openSUSE.*
Non commercial (community) support is offered by forums like Debian net, Debian Users, openSUSE Forums and Linux Mint.
* You can find more Linux distributions and reviews at Distrowatch.com