Windows XP has a built-in time synchronization feature that's designed to automatically synchronize your computer's clock with an Internet time server on a regular basis. To access this feature, double-click the clock in the notification area of the taskbar. From the Date And Time Properties dialog box, select Internet Time. Make sure that the Automatically Synchronize With An Internet Time Server check box is selected.
The Server drop-down list contains two time servers: Microsoft's time server at time.windows.com and the U.S. government's atomic clock at time.nist.gov.
While you can manually type the name of any time server that uses the Simple Network Time Protocol (SNTP) in the Server text box, it's more convenient to add time servers to the list. However, this feature is available only on stand-alone Windows XP systems or systems that are a part of a workgroup; it is not available on Windows XP Professional systems that are a part of a domain. Here's how to add time servers:
For a list of acceptable SNTP time servers, see Microsoft Knowledge Base article Q262680.
Note: Editing the registry is risky, so be sure you have a verified backup before making any changes.