Windows 2000 users will have to migrate to a more recent edition of Windows, such as Windows 7, but Windows XP SP2 users have a simple workaround: Install SP3. Doing so will grant you official support until April 8, 2014. Note that the 64-bit version of Windows XP does not have SP3, so support for XP x64 SP2 will continue until April 8, 2014.
If you aren't sure what version of Windows XP you're running, simply click Start, open Run, and enter winver. You can download Windows XP SP3 through Windows Update or as a standalone installer, though the former is recommended for home users. Microsoft has whipped up a comparison table of XP, Vista and 7 if you're looking for more incentive to upgrade.