Under Windows 8.1 and Office 2013 the Microsoft Upload Center 2013 (MSOSYNC.EXE) is started by a tasks in Task Sceduler, but it is not under "Microsoft" like some other Office 2013 Tasks (eg. Office 15 Subscription Heartbeat and OfficeTelemetryAgent).
I have the sceduled Task under "Task Sceduler Library" (above "Microsoft"), and there the tasks is called "Microsoft Office 15 Sync Maintenance for [MACHINE NAME - User]. If you check this task, you see it run "C:\Program Files\Microsoft Office\Office15\MsoSync.exe"
(I have 64bit Office) with a few different triggers.
It says very cryptical this task makes sure the cache for Microsoft Office Documents stays in good condition, and there is a warning that if you disable this tasks it can lead into problems when you work with online stuff ... well, it would be nice if they
instead could say in clear text what it does!
I do not have the sceduled task on all boxes, even if all boxes has Windows 8.1 + Office 2013 Pro (non subscription). I cannot at this stage say why not on all boxes, or what creates the sceduled task. Note that I do not have a "Desktop Skydrive" application,
nor am I logged in with Microsoft Accounts (only local accounts), and hence do not use the Skydrive App either.
It's up to you to decide if you want to try to disable the tasks in Task Sceduler, but it might come back by itself. The phenomen that some people have seen that it runs awhile and then disapears, only to run again at a later stage, is obviously because
it only does some maintenance tasks to this mystical "cache" and then kills itself. I asume it does only local stuff, and nothing on the Internet, at least not if not logged into Skyrive or your Microsoft Account when using Office. How could it? So, that the
task runs for a while now and then, probably isn't doing any big harm - except that it irritates you a lot!
As a sidenote one of the triggers by me is that it will next time run on 1st of April, which confirms the whole Microsoft Upload Center is a BIG JOKE? :)