Support for Windows XP ended at the end of April 2014. However, there is still a large base of PCs that are still in use running Windows XP. This is not good nor safe computing practice, especially if the PC is operating in a business environment and is being used for critical business applications.
ZDNet published an article detailing a simple registry hack (http://www.zdnet.com/registry-hack-enables-continued-updates-for-windows-xp-7000029851/) that will enable Windows XP PCs to emulate a Windows Embedded POSReady 2009 device. These devices are based on Windows XP, and are specifically used in basic terminal applications. The danger is that not all updates will be suitable for mainstream WIndows XP, and some critical ones may be missed. However, if you MUST run Windows XP for a really old legacy application, then there is still a way to obtain some update protection. It is highly advisable that you seek out a way to decommission your Windows XP PCs and replace them as soon as possible.
To enable this hack, add the following Key to the registry – HKLM\SYSTEM\WAP\PosReady
Then create a DWORD called “Installed” with a value of 1.
Alternatively, create a .REG file with the following text and merge it into the registry.
Windows Registry Editor Version 5.00
I will warn again that this should be a “I have no reasonable alternative” move. There are always other options, and the best option is to migrate away from Windows XP.