Sounds like the default time for Windows Update to run. I have Windows Update turned off.

>I think I've found it, accidentally. Was trying to set a scheduled task, and found a whole bunch of things that run on sundays 1:00 or such times, many of which were about what they mis-name "experience" (or at least think they use it in a meaning different from "practical knowledge gained over the years of trials, errors and frustration"). Just disabled all of them. Now I'm experiencing a few slowdowns from time to time, I guess something is complaining about a service or component not running, and tries to find it.