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:

  1. Launch the Registry Editor (Regedit.exe).
  2. Go to
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Current
    Version\DateTime\Servers.
  3. Right-click the Servers key, and select New | String value.
  4. Name the value 3, and press [Enter] twice to access the Edit String
    Value dialog box.
  5. Type the address of the SNTP time server in the Value Data text
    box, and click OK.
  6. Repeat Steps 3 through 5 for each additional SNTP time server you
    want to add, incrementing the value name each time: 4, 5, 6, and so
    on.
  7. Close the Registry Editor.

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.