Free clock synchronization utility software for windows

Maxiimus - Atomic Clock Synchronization Utility is a program that will query one of several atomic clocks operated by various governments and academic institutions using the Internet. You can then use these clocks to synchronize your Windows system clock. A scheduler utility is also included so that you can adjust your system clock automatically.

Network File Monitor Professional has an ability to extend its functionality by the additional modules like Time Synchronization Extension.
Time Synchronization Extension - allows to synchronize computers clock with Atomic Clock Servers.

Emsa Time Synchronizer is a very simple but useful time synchronization utility. Users that like simplicity,
may indeed like this program. Just one click of a button - and your computer clock is automatically set,
using an atomic internet time server. The program runs as system tray icon. It can be configured to run
automatically at Windows startup, and continously re-synchronize your clock at an user-specified time interval. Freeware.