WHY?
Why is Microsoft ending support for Windows XP and Office 2003?
In 2002 Microsoft introduced its Support Lifecycle policy based on customer feedback to have more transparency and predictability of support for Microsoft products. As per this policy, Microsoft Business and Developer products, including Windows and Office products, receive a minimum of 10 years of support (5 years Mainstream Support and 5 years Extended Support), at the supported service pack level.
Thus, Windows XP SP3 and Office 2003 will go out of support on April 8, 2014. If your organization has not started the migration to a modern desktop, you are late. Based on historical customer deployment data, the average enterprise deployment can take 18 to 32 months from business case through full deployment. To ensure you remain on supported versions of Windows and Office, you should begin your planning and application testing immediately to ensure you deploy before end of support.