Markus Selinger of independent test lab AV-Test has written a warning about the impending end of Windows XP security updates and summarizing their most recent test results for third party security suites for that operating system.
The useful parts of Selinger's analysis focus on the test data, part of which is embedded below. If users are going to stick with Windows XP past the support end date of April 8, 2014, then the quality of your security suite is crucial. Because there will certainly be new vulnerabilities in Windows XP that will remain unpatched you'll need other protections to keep them away from your computer. A quality security suite can provide these.
Selinger notes that the free options for Windows XP security are not the very best ones. The best of the free solutions, AVG Anti-Virus Free Edition, came close to the top, but G Data, Avira, BitDefender and especially Kaspersky's subscription products did better.
Selinger criticizes Microsoft heavily for abandoning XP users, a position with which I must disagree. Microsoft has been supporting XP for 12 years, far longer than any other vendor supports any other software product, and the core of the OS simply can't be securited to the degree that newer versions can. His point about Windows 8 usage share being (according to statistika.com) only 9% compared to XP's 21% misses the point that Windows 8 is relatively new and it's share is rising while XP's is dropping.
In fact, while you should secure your Windows XP system as best you can if you keep running it past April, you would be better off moving to a newer version of Windows, either Windows 7 or Windows 8.