Windows XP is as of April 8, 2014. Microsoft has tried to retire XP several times before, but due to enterprise customer demand had to continue supporting it. But this time they really really mean it, for reals.
If you're using Windows XP, it won't stop working. All this means is you won't get security patches or technical support anymore.
So what should you do? You can continue using it, as you always have. Or, you can upgrade to Windows 8.1, the newest Windows, or Windows 7. Or switch to Linux.