Support for Windows XP operating system is due to end during 2010 after a ten year lifespan, an extremely long time in PC software terms.
Windows XP SP 1, XP SP2 and Vista support will end during the year, and support will only continue if you are using at least XP SP3 or Vista SP1. Windows 2000 support will end altogether during July.
Microsoft believe that at least two thirds of XP users are not using any service pack whatsoever, so users of XP and Vist are being warned that their computers may be at risk, and that they should upgrade as a matter of urgence.
Given the satisfaction most users have expressed with Windows 7, and given that there are hardly any of the driver problems that beset Vista, most users would be advised to upgrade to Windows 7 wherever possible.