All of this that you guys wrote won't work on the Windows 7 / Windows 2008 Platform.
I have many Windows XP machines, and I time sync them using a GPS receiver. The machines get connected to that receiver using SymmTime, that's a software that won't work on Windows 7 / Windows 2008.
So what I did for the Windows 7 machine was just update it using time.microsoft.com (or another NTP server, it won't matter) but increasing the frequency of the update from once a week (Windows default) to once a day. I can visually notice that the Windows 7 machine has the same times as the other Windows XP machines that are time-synced using the GPS receiver.
Follow this guide to do the once-a-day time syncing with an NTP server on Windows 7.