After the April 8, 2014 some Microsoft products are no longer supported; Windows XP, Server 2003, Exchange 2003, Office 2003 … It is estimated that 30% of desktop operating systems are Windows XP.
Why you should be concerned.
Here’s a possible scenario. Let’s say that Windows 7 shares some code with Windows XP and an exploit is discovered that effects both. The security patch will be released for Windows 7 but not the discontinued Windows XP. Attackers can reverse engineer the patch to discover the effected code and then test the exploit against Windows XP.