Tomorrow is the last day that Microsoft will provide support for Windows XP installations that are running with Service Pack 2 [SP 2]. (Support for earlier versions has already ended.) This means that the only XP installations that will receive Microsoft support, including security updates, are those running Service Pack 3 [SP 3]. Using one machine here as an example, there were 46 security updates to XP in 2009, and there have been 26 so far in 2010. So using a machine that will no longer get updates does not seem to be the best plan.
You can get Service Pack 3 by turning on Automatic Updates, by visting the Windows Update site, or you can download the standalone installer. (The installer is fairly chunky, at about 316 MB. Microsoft says the installation from Windows Update is smaller.)
To check if SP 3 is already installed, click Start, then right-click My Computer and select Properties. If the update has been installed, ‘Service Pack 3″ should be listed under System.
I do strongly recommend installing SP 3 if you have not already done so.