Further research on Google yields the following information:
The mcupdate_scheduled task (in Windows Vista) downloads the following data packages. These data packages are used by Windows Media Center in Windows Vista; the same is probably true in Windows 7.
Directory Service: The Directory Service package lists the packages that are available in a region. The Directory Service package also provides information about how to obtain packages, about how frequently to download packages, and about when to download packages.
Client Update: The Client Update package contains updated regional information.
Sports (United States & Canada Only): The Sports package contains information about sporting events. This information is integrated with other Electronic Program Guide (EPG) information. .
Net TV (United States only): The Net TV package contains information about videos that are available on demand.
MCESpotlight: This package contains information about Online Spotlight applications that are available.
Since I hardly ever use Media Center - nothing wrong with it, I just don't use it - I'll ignore the error message and simply delete the schedule task. For as much as I use WMC, I'll update it manually.
The DispatchRecoveryTasks scheduled task launches:
%SystemRoot%\ehome\ehPrivJob.exe /DoRecoveryTasks $(Arg0)
Ehprivjob.exe is a digital cable device registration application. Apparently, this task is looking for a digital cable tuner, which I don't have and never had. I have a feeling that Windows didn't schedule this task on its own. It was probably scheduled by a third-party application, possibly a video player or video driver. If I can find the app and figure out how to disable the task, will do. Otherwise I need to find some other way to disable this scheduled task. Or I suppose I could also ignore it. But that's no fun.
Unless someone has further insight, I guess this will suffice as my question's answer.