This year there are a few versions of Windows which will go out of support. If you continue to use these version of Windows beware; it is effectively be the same as driving a Ford Capri around town; it works, everyone of a certain age knows what it is, but good luck if it goes wrong.
Windows 2000 Professional and Windows 2000 Server were both launched over 10 years ago and both products regardless of service pack will go out of support on July 13th, 2010.
Windows XP with Service Pack 2 will go out of support on July 13th, 2010; but support for Windows XP with Service Pack 3 will continue. This means that from July 13th onwards, Microsoft will no longer support or provide free security updates for Windows XP with Service Pack 2.
To ensure you still receive security updates, Windows XP should be upgraded to Windows XP Service Pack 3; this is available for free via the Windows Update website or from http://www.microsoft.com/downloads/details.aspx?FamilyID=68C48DAD-BC34-40BE-8D85-6BB4F56F5110&displaylang=en
Windows Vista with no Service Packs installed will go out of support on April 13th 2010.
To ensure you still receive security updates,Windows Vista should be upgraded to Windows Vista Service Pack 2; this is available for free via the Windows Update website or from: http://www.microsoft.com/windows/windows-vista/default.aspx
For more information and for further clarity, I recommend checking out: