Microsoft is asking all software developers to test their applications on the beta version of Service Pack 2 for Windows XP. This is because the new service pack, designed to enhance security, may not be compatible with all existing applications.
Tony Goodhew of Microsoft says: "It may surprise some of the developers that we are changing some defaults, and that may affect the way some of the older applications run." Microsoft has started an online training course to help developers out.
Goodhew adds that applications that don't work on SP 2 are insecure. SP 2 will focus on browsing security, memory protection, network protection and email security. it is expected to debut sometime in the middle of this year. Source