After that the time service will not do anything -- or run at all -- until the Task Scheduler starts it again.

This was tested on Windows 7 but should work with Windows XP and above.

I don't know about your machines but both my desktop and my HTPC have terrible clocks.

They seem to drift by about five minutes each week and that messes up things like scheduled TV recordings or stating that it is o'clock on IRC when it's not.

There is a Special Poll Interval setting under HKEY_LOCAL_MACHINE\SYSTEM\Current Control Set\services\W32Time\Time Providers\Ntp Client (note: it has moved at least once between Windows versions) which is the time (in minutes) between time syncs... While modifying that registry value may update the "next sync time" displayed in the control panel, I have found it does not actually affect how often the clock is synched.

Feel free to play with it if you want but that's my verdict.

As far as I can tell, the registry value changes how often the time service wants to sync but only applies when time service is actually running.When the time service runs is controlled by the Windows Task Scheduler, not the registry value, and (at least on Windows 7) when the service runs it exits immediately after performing any required work.Despite the apparent awfulness of PC clocks, Windows doesn't provide any user-facing options to change the clock-sync frequency below once a week.I've seen suggestions that you change the existing Synchronize Time scheduled task so that it runs more often. I tried making that task run once a day and my clocks still drifted.Upon investigation, that task simply makes sure the Windows Time service is running and if it's already running the task does nothing.In that situation it's still up to the Windows Time service when to actually performs a sync, which will be once per week.