If the Windows Time service is running on all your XP clients, you shouldn't need to manually synchronize. Your observation about Microsoft's support site is why I get so aggravated with it. You know the answer or the download is available, but their search engine is so unreliable. You can try and get really specific with your search parameters, and the engine just seems to ignore them. It's almost as if they want it to be difficult, so you'll contact their support-for-pay personnel. Anyway, here is a good white paper dealing with the Windows Time service.
http://www.microsoft.com/windows2000...intimeserv.doc
Towards the bottom, you'll run across some guidelines and commands to help you troubleshoot the time service.
Here's another small supplemental link (this is one you've most likely seen before):
http://support.microsoft.com/default...;en-us;Q216734
And one more dealing with the specific error message you wrote about
:
http://support.microsoft.com/default...;en-us;Q247321
I hate to quote support articles, but it's difficult to troubleshoot via a messageboard. I'm sure you're well aware that being a good network administrator doesn't necessarily mean that one knows all the answers, but where to find them. Lastly, another thing to check would be your firewall/router (if implemented). Check that UDP port 123 is not sealed off (or that another application is using it). More specific information regarding ports/sockets is in the white paper.
As a last resort, you could always just create a login script to do the 'net time' thing automatically.