It seems that Windows Update successfully pushes a WindowsXP patch to systems automatically, so that DST transition will be smoothly handled at the operating system level.

However, if you use Microsoft OUTLOOK and maintain calendar data (appointments, etc) you probably are well advised to visit the website below and follow through the "Wizard", proceeding approximately as follows:

1. Visit the URL, http://support.microsoft.com/dst2007 (USING INTERNET EXPLORER WEB BROWSER!!)
2. Click "HOME USER"
3. Click "Windows XP SP2" (should be the case for all winXP users, unless you know otherwise specifically)
4. Allow it to run the windows DST patch utility. Most likely it will fail, indicating you already have this update applied
5. On the next screen, specify which version of Outlook you are using (2003 most likely) and run the Outlook DST patch utility. It will prompt you to confirm your timezone, and will then summarize how many calendar entries it had to correct/update. You probably SHOULD review briefly (as it will suggest) that your data looks correct.
6. That is the end of the matter, hopefully! :-)